My favorite rooms to teach in have had drywall. The cinderblock construction of most classrooms gives them an institutional (in the worst connotation of the word) sort of feel. They lack warmth. They signify a lack of trust and care. A lack of trust in the sense that cinder blocks are more difficult to damage than drywall suggesting the students would damage anything less resilient. A lack of care in the sense that the people who constructed the building do not care enough to pay to add that extra amount which would make the place look nicer.
As a teacher, I would like walls that I don't need industrial-grade adhesive to put up posters or decoration. I would like walls that have some amount of insulation to keep out the noise from adjoining classrooms. And I would like walls that add a level of beauty to my students' daily lives.
This is not the solution to all of the problems that modern public schools face, but it's something that would make more of a difference than people might first think. People behave, react, and think better in beautiful surroundings. Drywall might not by itself make our schools beautiful, but it's certainly a step up from the cinder-block cells that our students usually see every day.