A British mother is teaching her son a lesson — by crashing his math class.

Becky Crandley, 30, punished her 12-year-old son, Harley, for his misbehaving at The Sittingbourne School in Kent by showing up on Friday to keep an eye on him, KentLive reported.

The mom of five said she decided to pay her son a visit after receiving a phone call that he had been rude to his math teacher.

“I constantly threatened that I’d sit with him in school if needed, and he always laughed it off,” Crandley told the outlet.

So with permission from his teacher, she showed up to join her son in class.

“He didn’t have a clue, and he was very embarrassed for sure,” she said. “I was introduced as his mom.”

Crandley said she doesn’t regret embarrassing him, though she wishes she had captured the moment on camera.

“If only I got a picture of his face when I walked in and sat down next to him. He went so red, there’s nothing I can compare it to,” she told the news outlet.