I was afraid my parents would find out
What would happen if they found out?
I know I would be severely punished
It's not good to disobey your parents, as they usually know what's best. In the future you shouldn't do things that that would make them want to punish you.
What is it I can do then? I'm stressed out and didn't feel like going to school.
I can understand needing a mental health day, but you should obey your parents. Talk to them so you can make them understand what you are going through.