A proposed bill to ban the discussion of homosexuality in Polish schools would violate free speech, a human rights group has warned.
Some 10,000 teachers marched in Warsaw on Saturday
Human Rights Watch (HRW) made its warning in an open letter to Polish Prime Minister Jaroslaw Kaczynski.
It also said the bill "would create a climate of intolerance" in schools.
Last week, Poland's education ministry outlined the bill to ban "homosexual propaganda" in schools and to sack teachers promoting such "culture".
HRW said the proposal would "punish anyone who promotes homosexuality or any other deviance of a sexual nature in education establishments".
"Schools should be training grounds for tolerance, not bastions of repression and discrimination," the letter said.
It also stressed that the ban "would deprive student of potentially life-saving information" on HIV/Aids.
It is the latest criticism of Poland's government for its alleged sanctioning of homophobia.
On Saturday, more than 10,000 teachers marched in the capital, Warsaw, protesting against the government's education policy and demanding pay rises.
The demonstrators demanded the dismissal of Education Minister Roman Giertych, accusing him of ignoring teachers' groups and increasing intolerance.
The conservative government champions family values and has called for "moral renewal" in Poland.
Mr Giertych heads the small, right-wing and ultra-Catholic League of Polish Families party, which has been accused of being homophobic.
The BBC's Adam Easton in Warsaw says homophobia is common in Poland, which is deeply Catholic.
But Mr Giertych's views are seen by many as radical and they have already got him into trouble in Brussels, our correspondent says.
In 2006, the Council of Europe threatened action against Warsaw over the sacking of an education official.
The official had been overseeing a Polish version of a Council of Europe manual on human rights education that contained a section on homosexuality and homophobia.