I think that for Math and Chem, the main factor will be the placement tests. My DS did a high school program in a university, took Calc I, II and III but did poorly in the Calc II portion of the test so was put into the Math 152 class. He did well on the Chem test and validated one year of Chem. He validated some more courses (without the placement exams) thru the 'A's that he got on those courses.
The credits will help in alleviating course loads later on. DS is planning a tech major with language minor and the academic plan he has shows he can still underload by one course each during all his 2deg and 1deg semesters.