Patrick Welsh ["Kids, Wired for the Night," Outlook, Sept. 4] has it backward. Teenagers stay up late because that's what their biology demands. Every reputable sleep researcher agrees on this, not just Brown University psychologist Mary Carskadon, who was quoted in Welsh's penultimate paragraph.

It is the school systems that are out of step with teen biology and that are making our adolescents arrive at school exhausted. If high schools started later in the morning, at times more in tune with teenagers' systems, adolescents could get more sleep when their bodies are calling for it.

Kids are awake late at night; they instant-message and play video games because they are up, not vice versa. How many teenagers do you know who get up at 5 a.m. to use their PCs? If electronics were an obsessive lure to sleeplessness, students would be up excessively early as well as excessively late, but that's not the case.

Before computers, my friends and I stayed up late in high school and in college, socializing by phone or in person or working on projects into the wee hours. Let's stop blaming snoozing students on bad parenting. School systems need to wake up and gear the high school day to students' most alert time, which is not early morning.

-- Sandra Evans

Falls Church

The writer is co-founder of SLEEP, a grass-roots organization that advocates later high school start times in Fairfax County.