The authors of Colours of the Rainbow, published this week by a London community health trust, say it "aims to affirm young gay men and lesbians within our society" and encourages teachers to accept that some pupils and adults in schools are gay.
They say it is the first classroom material of its kind to encourage an openly tolerant attitude towards homosexuality and is needed to counter bullying and prejudice against minority groups.
However, traditionalist pressure groups attacked the book, published by Camden and Islington health trust, as indoctrination and warned it could be illegal to use it in the classroom.
The 160-page book includes lesson plans under headings such as "the spectrum of sexuality" and "homophobia and its effects," and includes pictures of gay couples.
Suggested lessons include one for key stage 1 pupils, aged five to seven, which encourages them to view same-sex carers positively, and another for key stage 2 children, aged eight to 11, which aims to "give pupils an understanding of homophobia and strategies for coping with it".
Lessons for older children include a discussion of attitudes to homosexuals, and one which encourages them to choose captions for T-shirts which are positive about being gay.
Health worker Sandra Mole, the book's author, said it had been very successful in trials in schools in London and Winchester. "It's aimed at bringing about acceptance and tolerance and an understanding that we are all different and unique," she said.
"Young people need something like this in schools. I'm trying to give lesbians and gay people a place in society and this will give teachers tha material to do that."
Geof Ellingham of the School's Out teachers' group, welcomed the book. "It's a big step forward to tolerance. Children of all ages need to know about the range of different families and relationships. Many primary pupils will have come into contact with lesbians and gay men so they need to know what these things mean and that they are OK."
Liz Swinden, who helped research the book, said: "Teaching materials have assumed that everyone is heterosexual. The best of them have hinted that there may be people who are different, but this is the first time that homosexuality and bisexuality have been put on the agenda as acceptable alternative ways of life."
But Valerie Riches, director of Family and Youth Concern, said: "Telling youngsters about what is unnatural before they have any idea of what is natural is a worrying form of indoctrination. The message in this book seems to be that homosexuality is perfectly acceptable and that is dangerous."
Nick Seaton of the Campaign for Real Education said: "It is disgraceful that the NHS should be spending money on this kind of material. A lot of parents will be very disturbed. It could encourage youngsters to become homosexual rather than follow their natural development."
Valerie Riches said using the book in the classroom could contravene Section 28 of the Local Government Act which prohibited local authorities from promoting homosexuality. The Department for Education and Employment's guidelines say pupils should be encouraged "to appreciate the value of stable family life, marriage and the responsibilities of parenthood".
Colours of the Rainbow, Pounds 12 inc post and packing, from the Health Promotion Service, Camden and Islington Community Health Services NHS Trust, St Pancras Hospital, 4 St Pancras Way, London NW1 OPE.