Challenge always. That is where the fun is. There is no point in getting 100+ or 4.0+ - you want to be challenged - that's the learning zone; that's exciting. The student will have an easier time in their career(s) (my opinion). It is awful to see a colleague realize they are in over their head and were not challenging themselves from K through 12 or 16. It makes a difference in real life. There is a mental conditioning happening. For people who like cars, there are certain performance vehicles that are meant to be put to the test. For athletes, I think of an Olympian - they are not made in one year; they have ongoing physical conditioning. Go with what you think is right and how you truly feel most passionately. If going for the grades is what your student needs, then you don't have to listen to this response.