I went back to teaching when my son was 5 months old. My routine was to feed him in the morning when he woke up (usually right before I got in the shower). Then I got ready for the day and pumped at home right before I left for school at 7am. I pumped at lunch time (10:35 am) and my prep (1:25pm). I picked up my son by 4:30 and nursed him right away.
To be honest it was pretty stressful to give up all my non-student time to be pumping and then having to head out right after school, but it was worth it to my and my family.
A few things that made it easier/manageable:
*Hands free pumping bra (this was a lifesaver! I could eat my lunch and type lesson plans while pumping)
*I made a plan and THEN told my team and administrators the plan and what support I needed from them (ex. a para to walk my students to specialists so that I could have the whole 25 min prep for pumping) I think they would have been supportive either way, but one of my administrators doesn't have children and I think he was relieved not to have to talk about my lactation concerns with me
*An extra set of pump parts so I didn't have to find a place to wash and dry them at school. I just rinsed and threw them in a bag to wash at home.
*a double pump
*I pumped at home before I went back and built up a freezer stash, I didn't end up needing it, but it took the pressure off having to produce enough milk.
*I worked with lactation consultants when my son was first born (for latching issues- unrelated to going back to work) and they told me to make sure you do not lose your supply due to pumping (I was exclusively pumping for a month until we got the nursing thing going) to always pump for 20 min. You have 2 let downs, which many people don't realize, so they stop pumping after the first one, which tells your body you don't need more milk and so it produces less causing supply issues.
* our nurses office had a back room that I used for pumping. There was only one room though so I actually "shared" with another pumping colleague for our lunch break! We were friends, so it was okay, we just faced opposite walls and got over the weirdness of the situation. It was the only time of the day I got grown up time so it worked out
It's doable as long as you want to do it!