Venezuelan police have fired teargas to stop thousands of protesters against a new education law from breaking past a security cordon in the capital Caracas.
Protesters accuse the government of President Hugo Chavez of indoctrinating children into backing socialist values.
Health officials said dozens of people were treated for minor injuries.
Rallies for and against the law, which passed last week, have been held for over a week. Last Friday's protests also met a tough response from police.
Elsewhere in the capital on Sunday, thousands of Chavez supporters held a counter-rally.
They say the new law will give everyone equal access to education, regardless of their economic position.
The government says changes to the law - which among other things, broadens state control over schools and makes the education system secular - were long overdue.
But the Catholic Church and university authorities in Venezuela have opposed the law.
The government said protesters broke through a security barrier
The BBC's Will Grant in Caracas says some parents have threatened to take their children out of school if there is any socialist material on the new curriculum, while teachers' unions warn that they will boycott classes, and university students say they will stage further protests.
Analysts say parts of the law are open to interpretation and that it will only become clear how it will be applied once students return from their summer break.
The law requires schools to base their teaching on "the Bolivarian Doctrine" - a reference to the ideals of 19th Century independence hero Simon Bolivar, such as Latin American unity and national self-determination.
A previous attempt at education reform was one of the factors that led to mass protests in 2002, eventually culminating in a failed coup attempt against Mr Chavez.
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