Little kids wake you up in the morning and big kids could sleep through an earthquake, let alone an alarm. Every parent knows this.

Scientists know why. It’s the circadian rhythm that controls our internal clock. Before puberty it tells kids they want to go to sleep at around 7 or 8 o’clock, not that they always listen. After puberty the urge to sleep is delayed to 10 or 11. What doesn’t change is their need for a full night’s sleep, at least 8½ hours.

Here’s where adults come in. We decided long ago to make older kids start school earlier, so we could use the same buses that transported them to get their younger brothers and sisters, who start later even though they don’t need to. Early starts are considered too dangerous for younger children because it can be dark in the morning, especially in areas with long bus routes.

Over time, high school sports and other activities have become anchored to the afternoon hours. Employers have learned when to expect teenagers to be available. It works for everyone involved, with one rather large exception – the students themselves.

All the work that had been done since kindergarten to get children ready for school and eager to learn is undermined in high school by dragging them in and telling them to pay attention when they haven’t had enough sleep. Sleep debt, known as the “performance killer,” has been studied extensively.

A 2006 article in the Harvard Business Review offers this concise and troubling summary: “Stay awake longer than 18 consecutive hours, and your reaction speed, short-term and long-term memory, ability to focus, decision-making capacity, math processing, cognitive speed, and spatial orientation all start to suffer. Cut sleep back to five or six hours a night for several days in a row, and the accumulated sleep deficit magnifies these negative effects. Sleep deprivation is implicated in all kinds of physical maladies, too, from high blood pressure to obesity.”

Sounds like just what we want for our young people, right?

None of this is new, but the bad-old schedule has been depressingly durable. Not only have the afternoon hours been called-for by non-academic activities, doubling up on buses saves money. School districts this year – like every year – are facing tough choices at budget time, and no one seems anxious to invest in a later start for teens.

So, we are impressed that the Portland Board of Education is taking this issue on, but we’re concerned that they may go in the wrong direction. On Tuesday the board will discuss, but not vote on, five different schedules that would lengthen instruction time, as called for in the new teacher contract.

The schedule that is getting the most attention, because it’s the only one that fits in the current budget, would make a bad situation worse, starting the day 15 minutes earlier at Portland High School, moving the already too early start from 8 a.m. to 7:45 a.m., or about an hour before the body clock of a kid who went to bed at midnight might be starting to tick.

Longer school days are a good thing (sorry kids). But so is making sure older kids are in the right condition to learn.

The science in this subject is overwhelming. We hope the school board will consider it, and finally find their way to a later start for the teens who need it.