Smell of alcohol on breath, or sudden, frequent use of breath mints.
Abrupt changes in mood or attitude.
Sudden decline in attendance or performance at school.
Losing interest in school, sports or other activities that used to be important.
Sudden resistance to discipline at school.
Uncharacteristic withdrawal from family, friends or interests.
Heightened secrecy about actions or possessions.
Associating with a new group of friends whom your child refuses to discuss.
--From the National Council on Alcoholism and Drug Dependence