I have a few suggestions for you.
First, I paint my murals in Chromacryl acrylic paints. I buy them in bulk. When the murals are finished, I add several layers of Polycrylic, or a clear coat, to protect the artwork from bumps, and minor scratches, and also for better durability.
Second, let me share with you about my murals. I got my start painting murals a few years ago. I volunteered to paint murals at my high school after graduation. I painted a total of four murals, one for each of the foreign language classes. I did this over the summer. When the kids returned to the school the next year, they started to vandalize them. At the time, I had no clear coat on them because the work was still in progress. Everyday, I had to go back and touch up with the paint to cover up the writing and profanity. The administrators there were of no help. The vandalism continued. Finally, I finished the murals and put several layers of clearcoat on them. I went back to check on them a few months later and the kids scratched through the polycrylic protector, leaving my artwork marred. This didn't surprise me because it was a bad school to begin with. Well, I learned my lesson, I'm never doing another "free mural" again. People don't appreciate things they don't have to pay for.
I don't want to discourage your plans for painting at your school, I just want to warn you what the kids are like. I was crushed when I saw my murals (10 hours volunteered everyday for 4 months) being destroyed. I will never go through that again. I intend to start a mural painting business of my own in the near future, but this time, with a contract and a paycheck. No more freebies!
May I wish you good luck with your projects. Thank you!