Not exactly the same situation, but I'm a teacher and I went back to work when my first baby was almost five months. I kept her ebf until six months, and on my milk until she turned one. This is what my routine looked like at five months:
6:00am Feed on one side, pump the other
12:00pm Lunchtime at work. Pump both sides (if possible, sometimes I didn't respond well to the pupump)
4:30pmish At home. Feed on one side, pump the other.
Continue to feed on demand until bedtime.
7:00pm Bedtime. Feed, then pump both breasts
I was able to express enough milk for the next day, plus some for the freezer (by 7 months I was able to stop expressing at work, and by ten months I could stop expressing entirely). My lunchtime pumping session was only 15-20 minutes, because other people needed access to the stock cupboard (the only place with a lock!)
So. It is doable. If you want anymore of my anecdotal advice, I'm happy to help!