Ron Zodkevitch, MD, is a child psychiatrist and author of The Toughlove Prescription (McGraw-Hill). Do you have a parenting question for Dr. Ron? E-mail drron@familycircle.com.

Problem: "Brooke has a lot of friends, plays soccer, works on the weekends, takes AP classes and has always been an A student," says Kate about her 16-year-old. "But in the past three months she's become cranky, her grades have dropped and she's always tired-especially in the mornings before school. I'm scared she's on drugs."

Kid's perspective: "I feel bad when I snap at my parents, but I get frustrated that I have so much to do and can't keep my focus," says Brooke. "I really want to do better."

Dr. Ron's Diagnosis: At first I suspected drug abuse or depression, common causes for such new behaviors. A urine drug test came up negative, though, and my evaluation established that although Brooke was feeling overwhelmed, she wasn't depressed. Next I had her run down her schedule for me, and that's when I saw the problem-sleep deprivation. Like the majority of teens, Brooke managed her hectic life by cutting back on rest, getting 7 hours or fewer a night instead of the 8-1/2 to 9-1/2 hours that most teens require. Her grades were suffering because she was simply too tired to pay attention, especially in her first-period AP math class. Brooke's parents were considering punishment to force her to go to sleep at 10, unaware that a teenager's biological clock-geared to fall asleep later and wake up later-makes that very difficult. I suggested they take the following steps to help Brooke.

• Discourage overstimulating activities like sports practices, exercise or intense discussions in the hour before bedtime. All electronics must be off by then too. Brooke should instead use the time to meditate, take a hot bath or read for pleasure.

• Have Brooke scale back her superbusy schedule, making sure that completing her schoolwork and getting enough sleep take priority.

• Ease Brooke's need to overachieve by praising her for fulfilling her responsibilities and telling her she doesn't have to push herself so hard to excel at everything she does.

• Allow Brooke to sleep only two extra hours a day on the weekends. She needs to follow a consistent sleep routine to stay well-rested.

• Get the school involved by requesting that it take Brooke's sleep problems into consideration when creating her program. Classes that require her to be especially alert and focused, like math, history or science, should be scheduled at 10 or later, when her natural energy kicks in.

• Ban caffeinated drinks after noon and have Brooke avoid heavy meals or excess fluid two hours before bedtime.

• Keep cheese, bananas and milk available for snacks; they contain the amino acid tryptophan, which aids sleep.

Follow-up: Two months later Kate told me, "Brooke now averages about 8 hours of sleep on weeknights and even more on the weekends. The school switched her first-period math class with one third period, when Brooke is more alert. Her early class is now gym, which wakes her up." Brooke says she's feeling better. "At first I felt cheated by the new rules," she says. "Then I realized I liked not being so tired all the time." She also cut back her work schedule. "It makes sense to slow down," she says. "I want to enjoy my last two years of high school."

This story is based on Dr. Ron's case files. Details have been changed to protect the family's privacy.

Originally published in the September 2008 issue of Family Circle magazine.