No, they won't learn UNTIL it all goes BOOM! Then they won't be able to take registers, show pretty pics, or book their hols on line. Then they'll understand what you have been saying for years...

Don't forget that there may be good reasons why A/C is difficult, it uses a LOT of power for a start. If this is what is holding your school back, look at proper ventilation. Suck the hot air out of the top of the room and allow cooler air in low. This may help if the ambient air is at a suitable temp, even if it's not as good as real A/C.