Hijacking of schools for political rallies during school hours is irresponsible, said the Democratic Alliance on Wednesday.

Party spokeswoman Desiree van der Walt said the SA Democratic Teachers Union (Sadtu) was attempting to hijack schools for political purposes, and called on the ANC leadership to halt this.

"South African children already receive one of the worst standards of education in the world. Anytime that Sadtu takes from school time-tables to campaign for the ANC will constitute yet another assault on their dreams and their future," she said.

"This attempt to politicise schools will have catastrophic consequences for learning in general and for this year's matric results in particular," Van der Walt said.

But Sadtu's general secretary Thulas Nxesi dismissed Van der Walt's allegations as "cheap politicking", adding that the matter did not warrant being a national issue.

"That is cheap politicking by the DA because they do not refer to any incidents. There was only one Sadtu meeting that took place in a school in Daveyton and that was not a mass meeting," he said.

"It was held on a Friday afternoon and everybody knows that schools are already out at that time. We do not close schools. The meeting was held to discuss labour issues of Sadtu," Nxesi said.

ANC spokesman Carl Niehaus said the party was not aware of meetings held by Sadtu at schools during school hours. However it would not be in favour of such a practice, he said.