You can attend as many colleges as you want at the same time. There is no rule or law that says you cannot do this. It all depends on your willingness to do a lot of work and your ability to keep your schedule straight. I was earning a Ph.D. at one university and earning an MA at another in two separte fields. I never told my Professors until I was done with both. They just laughed and said, “That sounds like you.” But go for it.