What should I do if my friend thinks their house is haunted? My friend came to school crying because they were so scared!

Your friend needs to discuss this with his/her parents - there is little you can do other than reassure her. It's not your house.

They can't their parents will think they are crazy

Well, let's address Judy's first comment first. HAVE they actually discussed it with their parens yet or not? Because that really is the first thing to do. It is their children and their home and any help is going to need to be cleared through them. That's just the fact of it. Now, did your friend tell you why exactly they think their home is haunted? If so, what do they say is going on there?