Everyone keeps talking about "A" cdl. Where are there lists of "B" class schools? Since not everybody need an "A". Also looks good on a job application. Get a background investigation for an employer, so he will hire you.
Pretty much any school will do A B and C training, some will also do School bus specific. If your going to get a B you might as well just get the A and be done with it. The only reason to get just a B is if your already hired for a B job, or you have no intention of ever driving a combination rig. Of course once you start driving, you either love it or hate it. If you love it, you'll most likely want to drive a combination rig for no other reason then you enjoy it.