Truman and Tuesday are failing their cooking and tennis classes (Tuesday with cooking; Truman with tennis). They'll be forced to go to summer school if they fail their test. So their parents try to help them with those subjects. Mrs. X helps Tuesday and Mr. X helps Truman; the only problem is that Mrs. X, who is a good tennis player, turns out to be a terrible cook while Mr. X, who is a good cook, turns out to be a terrible tennis player!
