NSW Education Minister Rob Stokes took aim at the opposition leader's support of nationwide protests on Friday, when thousands of school and university students will demand governments take action to combat global warming.

By law, students are required to attend school on school days and by walking out of classes they're being "robbed" of education opportunities, Stokes said.

"The first part of leadership for a political representative is to uphold the law, and he (Daley) is failing to do that," Stokes told 2GB radio on Thursday.

"He is ruling himself out of being in any way competent of leading this state."

He also expressed his anger towards the international activists who think it's OK to tell children to not turn up to school.

Daley on Wednesday said global warming was the most pressing environmental threat of our time and young people should insist on having a voice where they currently have none.

He backed the thousands of students planning to protest and described them as "future leaders".

Friday's protests are happening just over a week before NSW voters head to the polls on March 23.