I too see nothing wrong with it. My dd7(soon to be 8) is close friends with a girl a year younger than she is - they are in a multi-age montessori classroom (grades 1-3). They are both rather introverted so I think it works out nicely. The girl was apprehensive about starting in this new classroom for first grade, and already knew dd, and dd showed her the ropes. They really really enjoy each other's company. As an aside, though I don't think it matters, my intuition tells me that this girl is pretty bright too (long story but I definitely feel that way about some of her other family members, though they're all in denial in that regard). Just the other day dd was saying that she didn't want to go to high school because then she won't be with her friends (lol) but I reminded her that they'll go to high school too.
I think that for dd, being friends with the girls a year younger in her class began as a way for her to gain confidence making friends. She started at this school last year for first grade, and while she loved it, she hadn't made any close friends (no birthday party invites, for example, until the summer) (she is extremely introverted).
I don't mind her focusing on younger kids at all; I think it's one of the benefits of the multi-age classroom and I sincerely believe that small age differences do not matter. (thinking out loud, maybe it makes it more like home - she is the oldest of five - though I'd hate to think that she bosses her friends around the way she does to her brothers!)
