It may sound dramatic but I have a question, an honest one.
Did they do ANYTHING correctly?
I’ve read:
They didn’t follow protocol
They mistreated Parents
They didn’t act decisively
The failed to stop the shooter outside
They didn’t communicate well
They didn’t move quickly
Etc
One non-Ulvade border control agent showed up and took care of business in short order.
So what did they do correctly, must be a few things?
Finally in regards to your question I don’t know. From articles like this the photos appear to show windows all over the building:
https://abcnews.go.com/US/security-measures-uvalde-school-district-place/story?id=84966706
If the classrooms had windows on the opposite walls from the doors, why didn't LE use them to take out the killer? He could only cover/control one of the 2 interconnected classrooms at a time. Perfect opportunity to shoot him through the window. Even an improvised mirror could have been used to peek inside the classrooms. That is, IF there were windows. If so, add the windows to the "missed opportunities" column.
Photo from Google street view. Robb Elementary School 715 Old Carrizo Rd, Uvalde, TX