Consider a temporary dip in grades as part of his adjustment if he’s just started junior high or high school. But if the drop in grades is dramatic and sudden, it may be a sign that your teen is depressed, abusing drugs or alcohol, or in some other kind of trouble.
Talk to your teen, with school officials, and, if need be, with a family counselor or psychotherapist to find ways to help.
If your teen has trouble making friends, listen and help him find ways to make contact with others (for example, participate in extra-curricular activities or youth activities) to give him more confidence and more joy in his life.
If your teen isn’t interested in school, your interest and involvement may help to make a difference. Participate in PTA activities, go to school games, encourage him to develop school spirit. When your teen sees that what happens is worth interest, he might decide it’s worth his interest too.