Bruises and injuries that your child refuses to explain. Unexplained crying spells before or after school. Withdrawl and secretiveness in excess of what is normal for children of that age. Rapidly dropping grades, missing homework, damaged homework, textbooks, or equipment. School supplies going missing constantly, with no explanation. Loss of appetite, refusal to eat, and preoccupation with ones appearance. There are probably more that I'm missing, but those are the big ones I remember.