Any experience with Dickinson rescinding an acceptance because of a D?

My son thinks he is going to get a D in an AP elective - Macroeconomics. He received his acceptance letter for ED today. Now he is worrying about being rescinded and I am worrying for him. Any experience or knowledge of how Dickinson is going to react to this D? Thanks.

He checked his school portal and he got a C. Woohoo, not the best, but better than a D. Yay. 8-|