Your child is a legal adult and responsible for all of their actions. The school cannot give you information about your child's grades or anything really unless your child signs a release form. The law is not concerned with the fact that you are paying all the students bills even if it is a very nice thing for you to do.
Your child has a problem at school. Should you call the school for them and try to work it out? NO call your child and ask them if they have spoken with the professor, the department chair, the dean, the president, in that order. If your child has not spoken to any of them what should you do? Tell your child to get their body over to the correct office and start asking questions (politely of course).
If your child says they have talked to those people and are getting the run-around have your child go to the office again and have patience, they need to learn how to deal with things.
Ok still no luck. Have your child provide you with the name and phone numbers and dates of the people they spoke with and then call asking if they are aware of the situation. Your last resort is to get involved.
Professors do not fail your child. Your child fails a course, ask your child if they went to class, how much time did put into the class, did they check with the professor (asking the last week of class what they can do to pass the class doesn't really count)? Did they seek help for a Teaching Assistant?