Approve comments across Multiple sites

Ok, just joined today and have been playing with all kinds of plugins etc but i still haven't found the one I want. I have a school blog (www.stjohnsblogs.co.uk) and then each class, and some pupils, have their own blogs too.
I would love to be able to have one place where all comments come to be approved without clicking on each blog manually. Is this possible?
Have I missed an obvious plugin somewhere? I have made it so that pupils can't see the comments on their own blogs so I need to be able to easily manage it for them before I create 200 blogs for all of the pupils in the school...

Thanks in advance!