About a year ago, Cody uncovered signs of the Google Maps app introducing special labels for School and Gym, similar to Home and Work. We didn't see those materialize for a long time, but over the past couple of weeks I've seen them pop up in Maps for me, either as a suggestion when adding a label or when requesting directions to the same place a few times repeatedly. The functionality isn't new, per se: I have vague memories of the labels showing for me many months ago, and I can spot it in the super old Maps v9.56. So it may have been triggered via a server-side update a few months back, or it could have rolled with Maps before v9.56. Either way, since we never covered it going live, I thought I'd let you know in case you haven't come across it yet.
If you ask Maps for directions to a place frequently, you might see a black pop-up asking you if you go there often and if you'd like to assign a label to it. Among those suggested are School and Gym with their special icons. You might also see these two suggested along with Home and Work when you try to add a label to a place.
However, if you apply either of these 2 labels, they will get the same generic icon as any other. The pretty graduation hat and dumbbell give way to a simple label icon, whether in the Your places list or on the map.
Also, these two special labels aren't treated as such anywhere else. They don't get an app shortcut on the Maps' app's homescreen icon and they aren't recognized in Assistant. Telling the latter to "go to school," "go to my school," "directions to gym," directions to my gym," or any other variation of those commands won't yield any appropriate response. Instead, it will search for any school or gym nearby.
It's clear that the functionality for schools and gyms isn't fully implemented yet, but the signs are more prominent now. Hopefully, these two labels will be treated like your home and work location soon.