I think it is very important that you have an interested preceptor and that it is made clear that you will be working together, not that the student will be taking the preceptor's work over for them.
On our floor we have pre-grad (3rd year) and 2nd year students. The pre-grads are buddied with a staff RN preceptor while the 2nd years have a single instructor for the gang of 8-10 of them. I find the days we have the 2nd years in become quite hectic as they essentially double the number of bodies on the floor and make things pretty cramped. Because of the low level of supervision I really keep an eye on what gets done and not done. Their instructor is quite good but she's only one person and bottom line, their patients are still your patients. Still I find most of them are quite good and I enjoy taking a bit of time to show them things if they come up and their instructor can't help them out right away.
The pre-grads are generally quite good. However I find that that they can get into a rut of just getting their work done if they're not motivated to learn more. As a preceptor I try to break down the specifics and themes behind clinical situations we encounter and go through it in detail when I can... time permitting of course
As a student I would suggest asking your preceptor / instructor / staff RN in a manner where you show them your knowledge level rather than asking to be spoon fed. For example instead of asking:
"What's this drug for?"
"I know this drug does ----- . Why are we giving it in this situation?"
This shows that you have put some effort into furthering your knowledge on your own rather than simply asking for the quick and easy answer. I think you'll find you retain things better this way too.
Hope this helps!