Can you really skip classes? What happens if you do?

So my friend said she had students being inappropriate around her and just decided not to go to that class for the rest of the year. Understandable.

but, when she said that, another friend casually said yea, and he has even done that before in a non chalant way.

Third friend said he had only done that when he had gnarly headache and took a nap in the nurse’s office.

I have never missed a class in 7 years lol made me wonder