Congrats on your decision to continue breastfeeding and congrats on your decision to return to school. I think it is great!
I went back to work when my son was 4.5 months old. I always nursed him right before I had to leave him with the sitter (sometimes even made her wait a few minutes for me so I could finish :o)).
I pumped once or twice a day at work - it probably took about 15 min each time. Sometimes I didn't get a ton, but other times I did better...just don't give up.
I also tried to see my baby 1/2 way through the day to nurse him again...
and I nursed as soon as I got him back...before I even went home.
I started pumping about a month or so before returning to work..so I could try to build up a supply.
I also pumped at night when he was nursing - both sides would always let-down, so I would nurse on one side and pump on the other. My hands were full! But I didn't feel like I was letting any good milk go to waste that way. I think I produced the most milk pumping this way.
Anyway...sometimes it was difficult and there were a few times when I didnt' know if I would have enough stored up for him, but we did it! He nursed until a few days before he turned one and he weaned himself!
And now he is one of the healthiest, smartest 2.5 year olds I know! (Doesn't every mother say that?!) :o)
Oh...by the way. I used an electric breast pump and pumped both sides when alone and pumped one side only when he was nursing on the other side.
I also found the best way to store milk (and unthaw it later) was to pump into a bottle (or whatever fits onto the pump), pour it into plastic breastmilk storage baggies (lansinoh brand, I think) - always in 4 oz and labeled with the date - and freeze it. You can freeze the baggies flat in the freezer and then stack them up so they don't take up much room. They also thaw easily by putting the whole frozen baggie in a cup of warm/hot tap water for a few minutes. It thaws out and heats up to the right temp within minutes! Remember to use the oldest milk first!
Best of luck to you!!