I have 2 busses, a rear engine diesel pusher with flat nose, and a front engine gasoline puller with conventional nose, and both are 96" from outer rub rail to outer rub rail. Both are Thomas Built Busses.
Bear in mind the fact that there are few roads in the country that school busses *don't* travel, and the fact that it has been only recently (relatively speaking) that vehicles over 96" wide were legal, and you can understand why the bus manufacturers haven't changed their tooling.
I doubt we'll start seeing 102" wide school busses any time soon.
If you want an bus that is 102" wide, I believe you'll need to go with an over the road coach bus, like a GMC or an MCI or an Eagle or one of the other big boys.
Hope this helps,