The union wants to ban the armed forces from recruiting in schools
Members were concerned that visits had risen sharply in recent years and that children from the most deprived areas were being targeted. Glasgow's Govan High, the conference heard, was visited 14 times in two years.
George MacBride, former education convener, said the UK armed forces had an "extremely bad record" in terms of recruitment policy, breaching international regulations designed to protect children.
"There are teenagers who have been killed during the (Iraq) war who should not have been there in the first place," Mr MacBride said. The armed forces seek to impress "immature" young people with a "highly skewed picture" of military life, he added.
A spokeswoman for the British Army said: "I'm quite disappointed because, as we've said before, we don't recruit children from school. All we do is give careers presentations and inform children what's available when they're old enough.
"All three armed services offer an absolutely fantastic array of careers opportunities and civilian qualifications, and the opportunity to do things you can't do in any other jobs."
Photograph: Mark Owens