Ask the teacher, but also give it more time. I think my daughter started talking about specific friends later in the school year, and asking if "so and so" could come over for a play date. Do you encourage play dates by inviting friends with kids his age over to play? Also, the comment about another child saying that he wasn't his friend, kids say that all the time if they are arguing about something or not getting their way. My daughter will tell me someone is not her friend one minute, then wants to have them over to her house the next day. Does he play with other children at the local park? or is he more shy around children he doesn't know? If you go to church, does he have friends there that he likes to play with? The more you can observe your child with other kids, you'll get the answers you are looking for. Get him involved in sports activities or whatever he is interested in to meet other kids (scouts, etc.). BTW, my daughter will tell me the same kind of answers when I ask her who she played with: "everyone", I found out being around other kids that some give more details about school than others. I found out alot about my daughter talking to other parents who would tell me what their kids were saying about mine. I'm sure he's still adjusting to the school environment as well, but always talk to the teacher about any concerns you have.