The science is clear — later start times are better for the brains of adolescents. That’s the consensus among experts, and the science is prompting school districts in this area and across the country to consider changing school start times to give older kids more sleep.

But what about the needs of those younger brains? They need quality sleep just as much as the older kids, according to Dr. Eric Zhou, a man who’s helped a lot of kids — and their parents — with sleep problems. He’s an instructor in pediatrics at Harvard Medical School and a staff psychologist at Boston Children’s Hospital and the Dana Farber Cancer Institute.

Zhou says that based on what we know about the sleep patterns of adolescents versus younger kids, it does make sense to start younger kids earlier.

“For the elementary age group,” he said, “it may be the case that [school] somewhere around 7:30, 8 o'clock in the morning is far more reasonable and aligned with their circadian rhythm naturally than for the high school age children.”

But Zhou kept returning to an unfortunate fact during our conversation about the sleep rhythms and needs of younger kids — there’s a ton we don't know.

“It's really hard to conduct a randomized controlled trial where you are intentionally keeping an elementary age child from doing something that they should do everyday, which is sleep enough,” said Zhou.

When considering the effect of earlier school start times on younger kids, there’s scant research. One very small study here in Massachusetts appeared to show a slight positive effect, and a larger study in Kentucky appeared to show a slight negative effect. But Zhou says the data points are too small and too different to be instructive.

Even if we can’t make scientific conclusions, we can make some real-life observations, in a place where they’ve actually made the shift, and there are actual students to observe: Harwich Elementary School, in the Monomoy school district on Cape Cod.

At the beginning of this school year, Monomoy moved the start time back by more than an hour, to 7:45 a.m. The teachers I spoke with at the elementary school are very happy with the change, like Katie Cloney, who teaches first grade.

“What we know, coming into school for years now, that the children come in very bright and very alive early in the morning, and when they are able to come in early in the morning their day is more successful,” said Cloney.

Melissa Brady, a kindergarten teacher who has been at Harwich 32 years, agrees. In the early morning, she said, “they are bright. Prime time is the morning for kindergarten students.”

The later afternoon, not so much. On the old schedule, “1:30, 2 o'clock, they were ready to stop," said Brady. "They were tired or they were frustrated, it wasn't a great ending to the day, and I've seen such a difference in that now.”

“We've found them to be very saturated and really after 2 o'clock not able to take in as much information as they had if they were coming in earlier in the day,” said Cloney. “Seeing the switch that we've done this year, it has made a big difference in our afternoons [with] meltdowns and behavior-wise.”

Now those kids are finished with school before that primetime for meltdowns begins. Samuel Hein, Harwich’s principal, says he’s seen a huge difference: fewer kids are being sent to his office in the afternoons.

“Just in the first four months, there’s a 44 percent decrease in office referrals,” Hein said. “Clearly there are no referrals after 2, because the school day is over.”

Hein added that as a result, the kids are spending more time learning. It seemed too good to be true, he said. “I was waiting the first half of the year for the other shoe to drop. Now I'm sitting there going, ‘No, really, I can be in the classroom. I can be around the building much more effectively and support the learning.’”

It’s important to emphasize that these are early findings, incomplete data, and just one school system and a small sample. And even assuming this is working well in the Monomoy school district, what works in Monomoy wouldn’t necessarily work the same way in Boston, or Middlesex, or Worcester.

But the parents and educators I spoke with agreed that getting this to work requires taking a lot more into consideration than just school start times. It’s not always easy for families — managing other kids, jobs, and transportation — to make the adjustments necessary to ensure those young brains get enough sleep to learn.

“I think the hardest thing that usually doesn't get discussed in the context of school start times and the impact on children is how does the school system or the health care system respond by adapting for the families,” said Zhou.

“You're shifting all sorts of different community supports,” said Scott Carpenter, superintendent of Monomoy schools. “When does the program at the town library that would support families after school shift forward — or what happens at your town recreational centers, or how how does youth sports get impacted, or the local dance, and what time are they can offer their courses to teach kids after school? It's something that the entire community has kind of evolved together.”

Joy Jordan is the parent of a second grader and a fourth grader, and she was initially opposed to the change, “thinking that it would mess our schedules up entirely.” She’s now an enthusiastic supporter of the new schedule and says a big reason for her change of opinion is the community support in place — the school worked with the local recreation department to add afternoon programs and transportation.

“They're activities that the kids can do from right after school until about 5 o'clock. And that has really helped kind of fill up that that longer afternoon spread that that we have this year,” Jordan said.

Maintaining the support requires ongoing adjustment, according to Hein.

“I'd say still almost every week there's some communication between the rec department after school program and parents being concerned about daycare options for their children,” Hein said.

No matter how well the schedules work out, the final measure of the start time change will be academic performance. We know that young brains that aren’t getting enough sleep simply don’t learn as well — so if the new schedule means the kids are not getting enough quality sleep, we could expect academic performance to suffer.

Given what he’s seen on the behavioral front, Hein says he expects to see the opposite.

“Traditionally, we've been introducing math in the later part of the day,” he said. “So by moving that earlier I haven't had the complaints about, ‘this is just overwhelming for the kids.’ We hope to see the results down the road relative to their student achievement.”

Policymakers in Boston and elsewhere may want to take note of those results when they’re available. While the particulars of each community create unique challenges, one lesson from Harwich might be that it takes a village to change a start time.