The demonstrators, including prominent conservative politicians and presidential candidate Karol Nawrocki, expressed strong opposition to the inclusion of sex education in the curriculum, news outlets reported.
The main slogan of the protest was "Yes to Education, No to Depravation."
Protesters said that parents should have the primary role in raising their children.
"We want to raise our children the way we want to, not the way the government wants us to," one participant told public broadcaster Polish Radio.
Many argued that the proposed changes aim to diminish the family's influence in child-rearing.
Prof. Zbigniew Izdebski, an educator, sexologist and coordinator of the team developing the new course, dismissed the protest as a misrepresentation.
He told Polish Radio that claims suggesting the new health education course would demoralise children were intended to provoke social unrest and exploit it for political gain.
Izdebski said the initiative is meant to provide students with scientifically grounded knowledge about health and well-being, not to undermine parental authority.
The plan has also drawn criticism from Polish Catholic bishops, who argue that the responsibility for sex education lies with parents.
In response, the education ministry has defended the initiative, saying that the subject is necessary to equip young people with essential knowledge about mental and physical health.
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Source: IAR, PAP, TVP