Family....I have 4 kids (9,7,6,&2) and a husband who works 60 hours a week - I feel your pain, lol!
You need to minimize and PLAN!! Minimize time commitments..... limit activities, and learn to say no when people ask for help (coaching, bake sales, car pools....whatever. if it makes your life harder, say NO).
Minimize cleaning...have your kids pick up some of the slack if you can. Depending on ages, they may be old enough to make lunches, help clean, do laundry. ... whatever helps! Hire a cleaning lady if it's in the budget...even just once a month is AMAZING.
Plan, plan, plan....every week on Sunday or Monday. .. look over what's going on for the week and get on the same plan with your SO. Have an idea of what time you have for kids, home and study. Stick to the plan as best you can!
Plan easy, quick meals and cook DOUBLE batches so you can have a quick pull-from-the-freezer dinner option ready to go at all times. Premake lunches and snacks for the week. I regularly make 50or so PBJ sandwiches at once and freeze them for lunches. Every Sunday I fill a snack basket in the fridge with bagged cut veggies, cheese sticks, baggies of lunch meat, pretzels, apple sauce cups, portioned nuts, etc... makes it super easy to pack lunches and grab snacks on the run.