Service learning in school, is it constitutional?

ok so i found out in the thirteenth amendment that involuntary servitude was prohibited. Which is what service learning is. The only reason I looked into this is because a radio personality from around my area talked about this and said that what the school is doing went against the United States Constitution. Now I just wonder if it is really true that this going against what is written in our laws or is there some kind of lope hole because I can't find one. What do you people think because I am not sure.