This is the best product I have ever found for putting up posters and student work on Cinderblock walls. Love the precut squares and it removes without damaging paint. One of the big rolls will last you the year!
StikkiWAX is amazing- I'm using it for my home office to hang stuff on the walls (paper, maps, calendars, ect) without having to put holes in the walls or damage the paint- it's WAY better than those 3M squares too!!