I already had my degree and then went back to take the prereqs for med school. I was married, and a "tad" older (24 ish). For both physics and chemistry...I went to the professors and talked to them about how serious I was. I asked them to supply me with the answers to the homework problems so I could be sure I was doing the problems correctly. In my opinion, there is no sense in "practicing" on homework problems and doing them incorrectly. So, I'd have the answer and I could work the problem until I got it correct. It took some convincing, especially with the physics guy...but he eventually did it. The chemistry guy had no problems with it at all. Also, at bigger book stores, there are problem books you can buy with answers. You have to look thru the books to make sure they are the level you want...but they do exist. I bought these for chemistry, physics, and biochem. I was not only studying for classes, I was studying for the MCAT at the same time, so learning the stuff was really important...I didn't want to waste time.
I can't really remember how we worked out my grades in those classes...perhaps went off the test scores alone, I don't know. However, I had one professor that said since he was helping me out, he would give me no higher than a B in the class - no matter what I did on the exams. I thought that was a good deal. I got an A...but a B went on my transcripts. However, that was fine, because it was more important to me that I understood and knew the stuff. Being a former teacher....professors/teachers sort of know which students are serious and which ones are blowing smoke. If you are serious, and you care about actually learning the stuff for the MCAT and not just passing the class and getting the work done...go talk to them and see if (if they won't give you the answers to homework problems that are assigned) - they will give you extra problems WITH the answers that won't be graded. I found the key to physics, chem, and biochem was PRACTICE and repitition. I am not a science nut by any means and I did extremely well.
Good luck.