I would pull him from that class and try to find another one. It's one thing to be in a class with larger dogs, but it's another to be in a class where the instructor does nothing to keep the smaller breed dogs safe. That's what ex pens and partitions are for. In the meantime, grab a copy of "Little Dogs: Training Your Pint Sized Companion". And, try to find some friends who also have small dogs or small pups that you can socialize your dog with. Don't give up - try these sites to find a competent trainer near you that can help:
www.trulydogfriendly.com
www.peaceablepaws.com
www.clickertraining.com
www.apdt.com
www.trulydogfriendly.com
www.peaceablepaws.com
www.clickertraining.com
www.apdt.com