In an exclusive poll of 700 teachers for The TES, 69 per cent of staff who teach 11 to 18-year-olds said pupils should be told how to terminate an unplanned pregnancy.
The survey, which also reveals teachers take a strongly liberal line on pupils learning about contraception and discussing homosexuality, sends a clear message to Ruth Kelly, Education Secretary in England, who is a devout Roman Catholic and is understood to oppose birth control and abortion.
In an interview last month, Ms Kelly said she stood by the Cabinet's collective responsibility over decisions to promote contraception. Sex education campaigners are concerned that her private religious views should not lead to changes in government guidance to schools. Overall, 59 per cent of all teachers supported practical advice on abortion being included in sex education.
Support was higher among headteachers and deputies than other staff, and more men (65 per cent) than women (56 per cent) were in favour. Teachers in Wales were less likely to agree that pupils should be given information about terminations, with only 47 per cent in favour.
Guidance from the Department for Education and Skills says covering abortion is optional and schools should respect the religious sensitivities of pupils and parents. It emphasises reducing pregnancy through contraception or abstinence and does not recommend telling pupils how to obtain an abortion.
A spokeswoman for the Family Planning Association, which advocates a "national curriculum" of compulsory topics for sex education, welcomed teachers' support for abortion information.
"People of all ages find it very difficult to know where to go in these circumstances. They don't know what to do, where to go, who to get help from," she said.Teachers were almost unanimous (98 per cent) in backing education about contraception, while 84 per cent said pupils should be told about the "morning after" pill.
The FPA spokeswoman said these topics should form the "core" of sex and relationships education, but in many cases schools were failing to teach them properly. She said: "It's about giving young people information and knowledge, but also developing the skills to consider their own attitudes and actions."
Most teachers said they would be happy to tell a pupil that it was all right to be lesbian or gay, with 74 per cent in favour (82 per cent among young teachers). Gay rights group Stonewall welcomed the "encouraging" response to what is believed to be the first research on teacher attitudes to homosexuality.