Non-religious cults

Has anyone else been in a non-religious cult? Do you ever feel like people don't understand how harmful they can be?

I was in a non-religious cult over 15 years ago and it still affects me today. The cult was a school with strange and extremely controlling rules. They tried to control when we slept, what we ate, our friendships, our personal lives, our beliefs and more. They wanted us to report each other for not being completely on board with the school's beliefs. People could be punished for weird things, like looking in a mirror without permission. They made us do things that were physically harmful and didn't believe us when we told them it was hurting us. We had to report our private thoughts and feelings to them multiple times per week, and we could be punished if they felt that we were holding something back. I could go on.