Do we ever see a picture of the outside of Wally's high school? We see Beaver's school, but I do not remember Wally's school.

There is at least one scene out there. It might have been in Wally's Orchid, where Eddie is trying to get Wally to ask Myra (played by the same actress who plays Mary Ellen Rogers) to a dance. All this is taking place in front of the high school (if I have the right episode).

Also when Wally goes to see Mr. Farmer the principal they show the exterior of the high school. (Eddie Quits School)

Not on topic, but IIRC a really good longer view of Grant Avenue School is shown on the school picture episode. Most establishing shots of that school just show the sign close-up.