The other posters hit the nail on the head when it comes to scheduling time to study. I think that the key is communication with your hubby regarding when you're really going to need backup. My best advice is to keep a planner with all of your tests and assignments, and that way you can tell the others on your "support team" that you've got a lot going on on specific days, and that you'll definitely need some help with the children on those days.
Little bits of time are like pennies that seem meaningless, but if you put them all together you can buy something awesome (like a sundae off of the McDonald $ menu
Use these bits of time to organize yourself, or even get started on assignments that "aren't due for awhile." Use extended breaks between classes, or if you get finished with a test early and have 20 minutes or so, use them to get actual work done. This also helps to take away the stress of the grouping and saying "what did you put for question 8?, Aww man, I thought it was C!" As a parent, you really do have to make the most of those little chunks of time. Sometimes my 1 and 3 year old will be playing together beautifully. I just keep my ears open, (and the eyes in the back of my head!) and let them do their thing
I don't know if I'm the only one who does this, but I LOVE to take my books to the bathtub with me
I don't feel at all guilty setting some time aside for bathing
This makes for long baths, but when I'm nice and relaxed in a hot bath, I get clean, AND I get some decent reading done. A little crazy, but I actually enjoy it!
Best of luck in your endeavors