Imagine you’re at a typical American high school. In one class, students line up at the exit early because they can’t wait to get out. Next door, honors students are engaged in a stimulating discussion until the bell rings. After lunch, a few of those students drive to their class at a local junior college, for which they’ll earn high-school and higher-education credits simultaneously. Some of these high-achievers might return home in the evening only to take another college course—this one a paid-online class—that their parents believe will help them get further ahead. Meanwhile, back at the school, the struggling kids are staring at computer screens, taking a remedial class. Maybe some of them lack Internet at home and can’t watch the video lesson their math teacher posted for homework. Over the weekend, an advanced student might meet with her SAT tutor, while her not-so-fortunate classmate could be washing dishes at the local restaurant.

Although these students might share a campus and a mascot, they form a distinct population within the public school, as is common throughout the country. This disparity between the relatively advantaged students and their disadvantaged peers often parallels that between private schools and public ones. In fact, the difference in opportunity can be surprisingly extreme within a single public school—sometimes even more so than that between the public and private ones.

Just look at SAT scores, which are one of the only measurements available for comparing public- and private-school students. In the middle-class California town where I live, the main private school (which charges about $12,700 annually for tuition) and public school have almost identical average SAT scores: 1830 and 1820 (out of 2400), respectively. But within the nearby public school where I teach, the gulf between the honor students and the rest of the school population is almost too vast to measure: The seniors taking AP English, for example, reported an average SAT score of 1890, while those in the mainstream English classes reported a mean score of 1590.

I wrote an essay back in March explaining that I opted to send my daughter to a small private school on the grounds that attending it reflected a “buy-in” rather than an obligation. I received a lot of critical feedback, including emails from a local parent who told me that my opinion was a “shame,” a teacher who called me “self-serving,” and a scholar who accused me of “white flight.” I anticipated their finger-pointing because I had already read a wealth of commentary related to the subject, including a highly circulated “manifesto” from Slate describing private-school parents as “bad people” and an essay on ABC.com arguing that enrolling kids in private school “sucks on many levels.” In one article about homeschooling, the journalist and author Dana Goldstein reflected a prevalent—though, according to researchers, debatable—sentiment when she concluded that pulling kids out of public schools “makes it harder for less-advantaged children to thrive.” Furthermore, I understood their complaints because I, too, believe a common and equitable educational system is integral to equality, democracy, and a sense of true community. As the U.S. Department of Education declares, “equity in education is vital because equality of opportunity is a core American value” and integral to the country’s economic strength.

But another popular approach among parents—enrolling a child in a public school while simultaneously investing time and money in extra programs to boost the child’s success and achievement—seems similar in its contribution to educational inequality.

When a child is participating in the public-school system, in theory he or she is thus supporting and benefitting from the broader goals of public education by promoting racial and socioeconomic integration on a single campus. But like students who engage in homeschooling or independent instruction, many public-school students at least occasionally leave the common group for additional outside opportunities: off-campus extracurricular programs, for example, or private tutoring. In themselves, these are worthy practices. It’s commendable when students and their families want to invest personal time and money in improving individual outcomes, and when schools encourage kids to take advantage of additional opportunities. But this can enable significant discrepancies because not everyone can afford, spend time on, or otherwise access those activities.

As a parent and high-school teacher, and a veteran coach of several sports at public schools, I am sometimes perplexed by the value in personal opportunities that are afforded more easily to some students than others. Is it better for my community if I remove my daughter from the private school and instead encourage her to take honors classes at the public school? Does that actually make a difference, and, if so, how? As a teacher, should I be excited for a student who dedicates hundreds of extra hours to private tutoring and club sports? Or should I be advocating instead for the underserved students who cannot afford the help and therefore find themselves at inherent disadvantage?

Participation in AP classes—which includes a third of Class of 2013 graduates—is one example. I taught AP English at a public school for eight years, and it was an entirely different world than the mainstream English classes I teach now in the same district. Similar to Goldstein, bloggers and parents who criticize the nature of private schooling often argue that it takes the best students away from the public-school system, at the expense of overall achievement at the latter. But within a public school, AP classes can do something similar, taking the more-advanced students out of the mainstream classes. The difference in the overall GPA between students in the 11th-grade AP class (taught by another teacher) and those in the 11th-grade “college prep” class (which I now teach) is significant: 3.68 and 2.90, respectively.  

A 2004 National Center for Education Statistics report, which found that students who took AP science and math had an overall GPA of 3.61, compared to 2.85 among students who hadn’t taken either course—even though AP courses are much more demanding. Likewise, graduates who completed an AP or International Baccalaureate class score significantly higher on the federal government’s standardized test. Plus, students who take an AP course are more likely to be surrounded by academically engaged peers, have the chance to earn college credit, and are often eligible for an extra point on the grade they received for the class (a 5.0 for an A, for example).

National statistics reveal that the student makeup of AP classes is not reflective of the school community at large, a reality that I’ve certainly witnessed in my time as a teacher. In 2013, students in the country who qualified for free or reduced-price meals, an indicator of poverty, represented nearly half of all high-schoolers but only 27 percent of AP test-takers. The College Board, which oversees the AP program, collected $350 million last year from the nearly 4 million tests that were taken. These exams cost students $91 apiece, though schools sometimes subsidize the fee.

Then there’s concurrent enrollment, when high-school students participate in postsecondary coursework on the side, often leaving campus to do so and getting a head start over their less-advanced peers. The merit of this extra learning is undeniable, but many students are barred from it because they lack the money or didn’t get the support they needed to get ahead. More than 1 million students took a course for college credit in the 2010-11 school year, and about half of them paid for their own tuition, fees, and books. Studies show that the individuals who participate in dual enrollment are more likely to both graduate from high school and earn a college degree.  

I know a student who took afternoon classes at the local community college last semester and ended up attending classes at his public high school for only 15 or so hours a week. This schedule is what educators might dub a “smart start.” And it is really smart. Along with his extracurricular golfing, he has already completed more than a year’s worth of college courses. He’s confident he can finish his undergraduate work at the University of California, Santa Cruz, where he plans on enrolling, within two years after enrolling. He’s friendly and outgoing, but how much is he integrating into the mainstream student population when he’s interacting almost exclusively with other high-achieving students and golfers, and spends more time on the college campus or at his job? Is this schedule conducive to the DOE’s goal of achieving “equity in education”?

A more-obvious discrepancy happens when parents pay for private tutors or test-prep courses. Private schools, according to the dad and blogger Serge Bielanko, “thrive because the other ones suffer.” But when parents pay for specialists to help their children excel at a standardized test such as the SAT, disadvantaged students suffer. The Atlantic has explored how the math section of the new SAT is particularly unfair to “kids who lack access to in-person test preparation” and “those who live in low-income housing.” And extensive research indicates that SAT scores correlate with family income. Nobody can track exactly how much money is spent on this extra help, but the revenue for test-prep companies and private tutoring is estimated to amount to the billions.

Even participation in club sports is an example of unequal opportunity. Athletic success in high school can help boost a student’s chance at being admitted to college and securing a scholarship. Participation in sports also correlates with academic success, including better grades and standardized test scores, along with improved health, concentration, and classroom behavior. High-school athletes are more likely to attend and earn degrees from college, “Most Valuable Players” even more so.

However, there isn’t enough room in athletics for everyone—in 2009-10, there were just 53 school-sponsored sports opportunities for every 100 high-school boys, and only 41 for girls, according to research from the University of Michigan. Given the limited access, it’s no wonder that millions of parents pay for extra coaching outside of school; participation on private club teams often boosts success in school-sponsored athletics. National data on exactly how many kids participate in private athletic programming is difficult to track down, but I can say that virtually every public-school varsity basketball player in my area—boys and girls—has played for a private team.

According to the Aspen Institute, parents of club players in 2013 spent an average of $2,300 annually per child on memberships, tournament fees, equipment, and travel—and more than $20,000 a year at the “elite” level. In theory, using a conservative estimate of $2,000 for annual expenses and multiplying that by the roughly 21 million youth playing sports outside of school, parents in the United States could be spending $42 billion a year on club sports. Just the travel alone for youth sports produces an estimated $7 billion in annual revenue, according to a 2013 National Association of Sports Commissions study.

Other examples are more politically charged. The Washington Post recently reported that “white parents in North Carolina are using public charter schools to secede from the educational system.” And The Atlantic has looked at the “cutthroat world of elite public schools in New York City,” where the NAACP is complaining of modern-day segregation because of the disproportionate racial makeup of eight of the city’s selective public schools. Apparently, the “sorting” of high- and low-achieving kids causes uneven distributions early on.

Likewise, opting kids out of government-mandated standardized tests—an increasingly popular practice among parents—can undermine equity in public-school systems. Last month, a group of civil-rights groups issued a statement in opposition of the opt-out movement: “When parents ‘opt out’ of tests—even when out of protest for legitimate concerns—they’re not only making a choice for their own child, they’re inadvertently making a choice to undermine efforts to improve schools for every child.” The group declared that the data from these tests is “critical for understanding whether and where there is equal opportunity.” As Andrew J. Rotherman noted in a U.S. News & World Report op-ed, many of the same parents who boycott these tests are “more than happy to opt their children in to the college gateway tests” such as the SAT.

When a public-school system based on equity and “equality of opportunity” is embedded within a capitalistic society, it can be a little disorienting for students, parents, and teachers. The DOE can proclaim its “twin goals of access and excellence” with a confidence in noble purpose, but when the system is constructed in a way so that individual motives incidentally hinder those who don’t have the same advantages, the compass can be difficult to read. But the conundrum of public-school inequality shouldn’t be ignored.

I sympathize with the New Jersey parent who, commenting on the practice of academic “tracking” in his daughter’s high school, was cited in an article as saying he could easily “look in a classroom and know whether it’s an upper level class or a lower level class based on the racial composition.” Tracking is a common process in which students are segregated based on their performance. A University of Colorado report bluntly states that while tracking is “rarely couched in the express language of race or class differences ... the preservation of privilege is always the subtext” of arguments in favor of it.

“You see kids entering the building through the same door,” the New Jersey parent said. Yet they enter a “second door,” he added, that’s systematically “stratified.”

If I, or other parents, are to eschew private schools for public institutions, how should we guide our children through that second doorway?