A couple of things. Does he have a co-exisiting learning disability that you know of? Has he ever been evaluated? They will not just "put him in special ed" nor can you request him to be put there. You can, however, request an evaluation to see if there is any kind of LD.
It is not true that "once their in special ed" its hard to get them out. Its not a different place, it's just support for a child who needs it. If he has a learning disability he may need services from the special ed department for his whole education. A child who recieves services from the special ed department is re-evaluated every three years to determine whether they are still eligible for services.
If the teacher is concerned, you could request an informal meeting with the teacher and special ed teacher. Usually the special ed teacher can make recommendations such as seating in the front of the room, extra time, or other modifications to help. If your son requires more help then informal modifications, you could request an evaluation under IDEA in writing. This will look for learning disabilities and other things that can interfere with learning. Then if he qualifies for an IEP or 504 accomodations, you and the rest of the team would meet to determine what form of help he will receive.
Here is a good site on education rights and the process for IEP or 504 plans:
http://www.wrightslaw.com/info/iep.index.htm
The kids that need help are placed in "the least restrictive environment" according to law. This means in the regular classroom with accomodations and modifications where effective; posibly pulled out for special help.
Some schools are really good with special kids and some are horrible. The worst are the ones that do not want to help with anything, let alone early intervention for the most benefit for the child.