Schools use report cards to let families know about a student's progress. The normal rating scale goes from an "A" down to an "F" or includes numbers, with 100 being a perfect score and a low of 60 usually meaning a failure.
When a report card arrives home, most parents take great care to read the entire document. Sometimes, a teacher will write comments that give specific recommendations or support for the child. Many times, a teacher will also explain why a failing grade appears on the form.