The college program is for college students who have completed at least one semester of college, the kids on that program are able to earn credit for school by taking classes while working at Disney. The classes are not mandatory, and not all schools give credit for the program.
The CareerStart program is actually very similar, except it is geared towords kids who have graduated High School within the last 18 months. There are classes as well, but these are required. You can do the careerstart program if you are in college, as long as you graduated high school less than a year and a half ago.
Let me know if you have any other questions.