AP Physics B does not exist anymore. It was replaced in the Fall of 2014 with the two year sequence AP Physics 1 and 2. You need to contact your school and have them change their course description.
If your son’s class is algebra-based, he is taking AP Physics 1 (first year of the sequence) or AP Physics 2 (second year of sequence). If his class is calculus-based, he is taking AP Physics C.