First New Generation Study Center http://www.fngcenter.com. should be a good one I guess. According to what I've heard of the center, they have the best facilities in W.Africa because the owner of the center is an American, The popular Mrs. Michelle, forgotten her surname now but any hoos, hope this helps. They have a 100% track record in processing foreign admission. The only problem I think they have is that they have only one center which is somewhere in GRA Ikeja. You can visit their site to get the breakdown.

Peronally though I don't really like Americans taking up our business here in Nigeria but hey, what matters is 100% service delivery!

Yup, GIEVA takes good care of this. For Tutorials and preparation for SAT GRE GMAT etc, I would recommend http://www.fngcenter.com. Hope this help