Parents were outraged Sunday to learn that authorities are keeping under wraps crucial information about deadly weapons found in city public schools.

“Mayor de Blasio is violating the trust parents place in his administration to tell the truth about whether their children are in danger at school,” said Jeremiah Kittredge, CEO of Families for Excellent Schools.

The anger came in response to a Post exposé Sunday that revealed parents had been kept in the dark about a frightening uptick in weapons confiscated at schools.

The number of deadly weapons confiscated at city public schools increased 26 percent, from 1,394 to 1,751, between July 1, 2014, and May 8 this year, compared to 2014-2015.

“Instead of recognizing the voices of parents who have been calling on the mayor to address a growing crisis of school violence, he has chosen to systematically deny that weapons and violent incidents are going up — both of which we know now are undeniably true,” Kittredge added.

Sam Pirozzolo, vice president of the New York City Parents Union, called the growing number of deadly arms at school “a ticking time bomb waiting to explode.”

“We should thank God we haven’t had any shooting in schools,” he said.