In all fairness, they shouldn't treat it so much like them doing anyone a 'favour' it's more so them helping people while having a holiday, so long as they actually do a decent job, who cares if it isn't as efficient as giving the money away to charity, chances are when you give consideration to the money they would have otherwise donated to charity as opposed to going on holiday, the end result is more beneficial to the people wherever they go if a group of unskilled students do go and put a bit of effort in although it may be pretty much a holiday than if they were to simply donate money.