I'm doing it now! I am due in a few weeks with #5, and my others are 14,11,6, and almost 3. I won't sugar coat it, it's not easy! My husband works evenings, so I'm almost always here alone with the kiddies for dinner/baths/homework, and I'm in class during the days (and he's here with the toddler). I study while the older ones work on their homework (give toddler a coloring book and let him do his "homework" too), study after they go to bed, study during commercial breaks when we're watching TV together (lol), and anywhere I can get even 15 minutes to spare.
One thing that has helped a LOT is that I go through my notes, type up the important points (before a test) and have my daughter (11) read them to me as we drive around town on errands, while I'm cooking dinner, sometimes while I'm in the shower, etc. She loves helping me study, and it's like having my own little audio book of my important notes. This may or may not be an option for you given the ages of your kiddies and whether or not they'd be interested in helping, but it has helped me a great deal.
I have As in 2 of my classes and a very high B in the third at the moment (only 3 more weeks to go in the quarter) so I have to say so far, so good. Again, it's not easy and I do lose some sleep to study sometimes... the stress level is definitely high, and the house is not nearly as clean as it should be.