Do you have a nice modern reference where I could find the computation of $H^2(S_n,\mathbb{Z}/2\mathbb{Z})$, where the action is trivial ?

I have looked at the very few books on cohomology of groups I have, but I couldn't find anything. The only reference I know is Schur's original paper, but it is written in German, and the style is quite old-fashioned.

I cannot imagine there is no modern book including this computation...

Thanks in advance for your help.

Greg