Teenagers don’t just look sleepy in the morning, they really are.

When they hit puberty, the internal clock that governs the internal rhythm that tells them when to go to sleep and when to wake up goes haywire (like so much else).

So while a grade-school child gets sleepy at 8 or 9, his older brother will just be getting going at 10 or 11. And since teens need at least nine hours of sleep each night, they are not going to be too chipper when they get up in time to get to school at 7:30 or 8 in the morning.

This grogginess affects learning. Teens don’t absorb as much information early in the morning, they don’t engage in spirited discussion and they don’t perform as well on tests when they are dragged to school so early.

All of this is beyond question. But worth questioning is why, in spite of all the well-documented evidence, do we adults insist on sending teens to school early in the morning?

It’s not because it helps them learn. It’s done because it accommodates school districts’ bus routes, allowing drivers to drop off high school students and loop back for the younger siblings who start later.

Sports programs have built schedules around the early start — and early dismissals that go with it. Fast-food joints have come to expect their workers to be available by early afternoon.

The districts do it because that’s what they have done for a long time.

Congratulations to Portland School District officials who are asking the right question: Does it make sense to keep dragging teenage students in early every morning?

The city is considering a new school schedule that would not only bring high school students in at 9 a.m. instead of 8 a.m., but would also keep them another hour later.

That might interfere with sports or jobs or after-school naps, but it makes a lot of sense. If scientific research says early morning is a bad time for student learning, why are students in school then?

The proposed schedule is bound to be controversial. It calls for shortening vacations, collapsing two second- semester breaks into one in March, which would put the city out of sync with most other schools in the area.

Some parents and students will likely complain, but at least Portland is asking the right question. If teens learn better later, stop dragging them out of bed so early.