I have a 5-year-old and a 2-year-old. On days where my older daughter was in kindergarten (she's going into 1st grade in September), I studied when my younger daughter napped, and then again when they went to bed. They go to sleep no later than 8:30pm, and then I usually do a quick clean-up of the living room/kitchen (no more than 30 minutes), and then study from 9pm until I'm done. There were some very late nights for me. In addition, on one of my husband's days off, I go to campus and spend several hours in the open lab, take a break for lunch, and then hit the library for several hours of studying. I always have flashcards on a ring with me, and I study them while at dance class, or in the waiting room at the pediatrician's office, etc.
On days where my oldest is home, I still study during naptime, after setting her up with a snack and a quiet activity (coloring, Playdoh, beading, etc). Once she was reading better on her own, I'd print out fun worksheets for her, and we'd both sit at the table and do our schoolwork together, which she loves. My husband has had to step up a lot with the housework, which he doesn't love, but we both know it's not forever that I'll be so busy. I try to do a mommy-daughter date with each of the kids once a month, because I know it upsets them sometimes that I am gone/busy so often.