My older daughter took Math 1B and Math 2A (second and third semester of Calculus) at a local college when she was a high school senior. AP calculus is the highest math class offered at high school. She took the classes for credit meaning taking tests and have a grade on her transcript.
My feeling is that teachers are better at junior college than those of AP calculus at high school. Students are more serious too because those in Math 1B and 2A class plan to major in science/engineering and to transfer to University of California systems. In general, she had pretty positive experience.
If you plan to show the college transcript to other institutions during college application, then you need to consider the grade that he may get in college class. Keep in mind that universities want to see that a student takes challenging classes and gets As.
I would not too concern about him taking the class again down the road. If he plan to major in any science, he probably need to re-take biology or chem or physics class when he gets to university. Junior colleges and high schools usually do not have the same resources. Math may be different since no costly lab is needed.
