Youngsters who dislike school are twice as likely to be involved in under-age drinking, research suggests.
And the more young people drink the more likely they are to have sex, it adds.
The study of 3,641 11 to 14-year-olds by a team at Liverpool's John Moores University suggests those drinking once a week are 10 times more likely to have full sex.
And it found links between general unhappiness and alcohol use.
The findings suggest that children who did not feel school was a nice place to be were twice as likely to drink and two and half times more likely to engage in sexual activity - including kissing, touching and full sex.
The youngsters were also asked about their general well-being - how they felt about their looks, how well they got on with their parents and their teachers.
'Hardest to reach'
The study, published in the journal Substance Abuse, Treatment, Prevention and Policy, says those with an unhappy home life and those unable to talk to their parents are also more likely to drink.
The findings by the team from the university's Centre for Public Health also shows a strong link between alcohol and sexual activity.
Children drinking once a week or more are 12 times more likely to engage in any sexual activity, and have 10-fold higher odds of having sex, it adds.
Lead researcher Professor Mark Bellis said: "Our study identifies that the children who drink and are sexually active are also more likely to be unhappy with their school and home lives.
"Such children can become disengaged from both family and educational support and risk progressing to sexually transmitted infections, teenage pregnancies or becoming an alcohol related casualty at an accident and emergency unit.
"This study paints a clear picture that the children we most need to support are often the hardest to reach through conventional educational and parental routes."