Assigning More Than One Course at a Time

Can I assign more than one course at a time to a class? Some of my students get done much quicker than others, for example, I had a few students get through Lesson 1 in 12 to 15 minutes and then had a few who took all hour and still didn’t complete. I want to assign a second course of a different level to offer some additional work for students who complete so much faster than others.