(CNN) President Donald Trump grew indignant on Thursday in opposing "active shooter drills" in schools, making a rare reference to his own son as he described the practice as "crazy."

"Active shooter drills is a very negative thing, I'll be honest with you," he said at the White House. "I think that's a very negative thing to be talking about. I don't like it. I don't want to tell my son 'you're going to have to participate in an active shooter drill. I'd much rather have a hardened school."

Trump's youngest son, Barron, is 11 years old.

"I don't like it. I'd much rather have a hardened school. I don't like it. I wouldn't want to tell my son that you're going to participate in an active shooter drill," he said.

"I think it's crazy. I think it's very bad for children."