Okay, I’ll qualify the statement. “It would be the first time I’d ever heard of a school rescinding an admission because someone dropped a single AP class.” That’s why the call to Rice needs to be made. Being rescinded is usually related to low grades, cheating, criminal conduct, failure to complete admission requirements, or some other obvious violation of the agreement between the student and the school. Comp Sci (AP or otherwise) is generally not an admission requirement - certainly not at Rice. Possibly, they are concerned that he is failing the course and want more info. Only a call to the school is going to clarify the situation and, if Rice is actually threatening to rescind because of a dropped AP, it would be important to understand what the rational was.