In a freshly painted fifth-grade classroom, Natalie Klem sits with a group of teachers planning an orientation for next year’s incoming class at Lead Prep Southeast in Nashville. It’s the beginning of July, and she’d had her “last day” of school just over a month earlier.

“I can’t remember the last summer I didn’t work,” says Klem, who’s been teaching math for six years in public schools, both traditional and charter. Klem typically tries to spend most of June completely disconnected; she avoids answering emails, developing plans for the upcoming year, and spending any time on campus.

“But that’s not what actually happens most of the time,” she says.

Teaching entails a schedule unlike that of most other careers. Ostensibly, the typical teacher in the United States works 180 or so days annually, which comes with an average starting salary of a little over $36,000. But that excludes the work that he or she probably does throughout the summer, after school hours, and on the weekends. That 180-day policy is also a measure of the amount of time students—not necessarily teachers—must be in school. It doesn’t take into account professional-development time, parent-teacher conferences, and “in-service” skills-training days, for example.

Because of the low starting salary, teaching is considered a poorly paid profession compared to other careers involving similar background and education requirements, such as registered nurses or accountants. Arne Duncan, the U.S. education secretary, has said that public-school teachers are “desperately underpaid,” and has advocated for doubling their starting pay.

“Most teachers do need the extra money and they do work in the summer,” says Richard Ingersoll, a professor at the University of Pennsylvania’s graduate education school whose research focuses on the teaching force; he cites data suggesting the majority of them even get actual summer jobs. According to Ingersoll, the average teacher’s earnings (including any money earned through summer work) are still lower than that of other professionals even when accounting for time off. And several studies have shown that low salaries are a top reason teachers leave the profession.

Still, research on the adequacy of teacher pay is adequate has gotten mixed results. Jason Richwine, of the Heritage Foundation, and Andrew Biggs, of the American Enterprise Institute, have argued that teachers are overpaid—or, at least, aren’t justified in complaining about their salaries—citing that a teacher’s salary amounts to about $1.50 for every $1 that they could earn in a private-sector job and that their skill sets are more limited than that of the average worker.

Another one of the main reasons cited by Richwine and Biggs, among other critics, is that teachers enjoy a big break each summer.

It’s true that, relative to employees private-sector careers, teachers in America tend to work fewer days. According to a U.S. News and World Report op-ed arguing against higher teacher salaries, the average private-sector employee works 260 days a year, while the average appears to be slightly less than that for public-sector employees. But educators like Klem tend to agree that having an extended break from classroom instruction (as opposed to paid time off here and there) makes the challenges of the job more manageable. And that break from instruction doesn’t always mean a summer vacation of idle R and R.

For the most part, the charter school at which Klem currently works follows Tennesse’s traditional public-school calendar, only adding a few extra days at the beginning of the fall to include the time teachers spend in professional development before students arrive. But again, that calendar doesn’t factor in the summer hours. Klem says she’s spending the rest of her summer this year attending meetings, developing school curriculum, helping train new teachers, and contacting families of her students, among other tasks. Past summers, she says, have been equally busy: graduate-school coursework to complete her master’s degree (which isn’t required but can mean higher pay), classroom organization or relocation, and so on. While some of these responsibilities come with a stipend, teachers say they’re relatively negligible given how much time they take—no more than $1,000.

The relationship between summer vacation and compensation is complicated. According to Ingersoll, the original school calendar was based off of that used for agriculture so that kids could help on the farm. The logic was that teachers only worked the amount of time that kids were in school, so it theoretically made sense to pay them less than if they were a full-time worker. But, with the modern economy, proof that teachers work much more than their work year accounts for, and the push in many school districts toward extended days and years, the teacher-compensation question has become increasingly complex.

Regardless, it’s a well-known reality among teachers that even though they’re expected to put in extra time and energy throughout the school year, their salary is what it is. Alex Turvy, for example, sees summer time off and his salary at the New Orleans KIPP school at which he teaches as disconnected elements that are hardly within his control. “It’s sort of fixed,” he said when asked about his pay, doubting that many teachers would be pushed to perform any better than they are now if their wages were higher. According to Turvy, his colleagues are “motivated by wanting to do right by their students.” In fact, he said he doesn’t even think about his pay when it comes to his summer vacation—a period he considers as his time to recharge, reflect, and step back. Indeed, burnout is a widespread concern in the teaching industry, and a common reason why teachers leave the classroom.

Meanwhile, teaching salaries are often tied to contract pay schedules with little to no room for negotiation. The majority of districts will use a “salary grid” or a “uniform salary schedule” that establishes salaries based on number of service years and level of education as the sole factors determining pay. Rarely do a teacher’s specialization or qualitative performance in the classroom factor into salary. “It’s a no brainer,” said Dr. Ingersoll, commenting on how teacher salaries work. “Quality and performance aren’t taken into account … [But] we all know some teachers are far better than others, we all know some teachers work harder than others, and of course it’s unfortunate that these differences aren’t recognized in the salaries.” Yet even despite new efforts at reforming teacher-pay systems, it’s unclear how the typical teacher summer will, if at all, evolve.

Ultimately, few teachers are optimistic that anything will change. “At the end of the day,” Klem said, “you definitely don’t do teaching for the money and I realize that.”