Hi R.,
The other ladies who have responded are right on track! I have two boys. One is fabulous and doing very well in school, did very well in pre-school. My younger one just started pre-school/daycare and is where the other kids are but I see him learning new things every day.
Kids learn differently and they are all their own individuals. It's so important to remember that. If the teacher makes you feel like he's not doing well, talk to her again. This should be a time of play/learning and fun - not just a lot of learning. They are children.
What one of the other Mom's said about how some are in daycare since day one and yours just started - of course he might be a little behind the rest, he's still adjusting to their way. He will be just fine and actually sounds like he is doing really, really well.
If you really are concerned, you really should talk to the pediatrician about it - they know where your child should be developmentally.
Hang in there! You know him best and will do what is best for him.