Ugh. This is one of those things that reasonable people can have different, valid opinions.
Veterans benefits, for examples, seems to be crying for an apostrophe, but the U.S. Veterans Administration does not use one.
I would suggest using it attributively because it will save you trouble and awkwardness in other situations. You won't have to write things like "The Nursing Mothers' Association's weekly outing" or whatnot.
- For Teachers