Starting school just 30 minutes later had a significantly positive impact on students' health and test scores, according to a new survey written up by the Wall Street Journal. This is not new news. Nor is it news to education mavens that ending a few hours late, as KIPP schools have done for years, has correlated with higher achievement scores, especially in low-income areas.

So would late start/late finish be a smart model for urban and/or suburban elementary and high schools? To think through the issue, I spoke with Frederick Hess at the American Enterprise Institute. Here's an edited transcript:

You've read the WSJ article. Do you buy the evidence that a later start time would be better for high schoolers?

There's been research suggesting this for decades. In the D.C. area, say Montgomery County, you have parents pushing for this every so often. More sleep makes good sense given physiological development. It's not clear how much of a difference it would make on test scores. If you start later, kids might go to sleep later, maybe goofing off online, and it's not clear how this would work out in practice.

Would there be logistical challenges to a later start time for high schoolers?

You'll have to dramatically increase outlays by expanding bus routes. You have staggered attendance for high school and middle school. One reason for this is that older kids have to get to school first because we're worried about having little kids outside waiting for the bus too early in the dark. The only way to change that is to buy more buses to transport more kids and the same time.

If there are good reasons to start later, and good reasons to finish school later, is it fair to say we should think about shifting the entire school day back?

There is a push to extend school hours, later into the day or have kids attend part time on Saturdays. You're talking KIPP (the Knowledge is Power Program created by Teach for America alums), which is about 8AM to 5PM. But that's distinct from adjusting the window of school.

If you want to start at 9, that gets you to 4 or 4:30PM. Extending the school day until, say, 6:00PM would gut extracurricular activities, practice time for sports, and game time. It then puts the notion of extending the school day in conflict with other things than suburban families value.

It depends on the context. In an urban environment with limited extracurricular activities, certainly people are talking about those things in conjunction, to have kids constructively engaged for longer hours to keep them out of trouble. In suburban pockets, you're running up against the political will to protect extracurriculars parents value.

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