Get up on time, and go to school. Your mom is doing nothing wrong as she's just concerned. Come on, if you were a parent, and your child was failing most of his classes, not going to school on time, and pretending to be sick, not going to school at all, what would you think?

Not hard to figure out why your mom is getting mad, so I suggest you apologize, go to school on time, and bring your grades up. Your mom and no one else will do that for you, so do it.