Go to the State of Michagan Education website and search student class size. If you do not find an answer, call the information line, or send an email to find out. They will know.
As for the teacher, she has 28 other children coming in the morning, and that probably means that she has more than 50 families to accomodate and plan for. She may be trying to get enough desks for them and find someone to bring them from central storage, and figure out how the old style desk will fit in her little room. She also probably has more meetings than you can shake a stick at about things like the schools best practice, the new email system, how to use the new copier (becasue she is not alowed to touch it until she does,) a seminar on the new IEP forms the district is using...she may have children with special needs and was sent to a conference so that she could be "highly qualified" to teach them; if that was your child, you would be very happy about that, and would be able to sue her if she didn't. You just don't know how full a teachers life is these days. I would be willing to bet that there is nothing that your son's teacher would like more than to be able to meet each and every one of her students such that their experience was good, but it may just be imposible. Being with your son and teaching him is exactly why she went into education.
Many teachers are not even in the classroom untill a day or two before school starts, so it is likely that she has not even accessed her school email, even if that system is up and running like the communications support director promised last spring, because it probably isn't quite right yet.
Try to realize that every parent feels like you do, epspecially if this is your first child. As strongly as you feel, it is not an emergency, and it won't gain you enough to make it worth it to get off on the wrong foot with this very special teacher. That is what kindergarten is, very special, and you should love his teacher as much as he does. If she could respond, she would have already. If she doesn't, assume that she can't and make the day as special as you can for your son without a personal visit with her before hand. It will be OK, either way.