What I am curious about are your experiences for highschool. Thinking of what she will be exposed to as a 13 year old freshman-not driving until her senior year-will she be able to maintain friendships being so young. Will she be ready for that? I know you don't know her but if I could have some personal experiences to feed off of I think it would make this decision a little easier.
My son is 13 (fall birthday) in 8th grade, but taking two freshman classes so I can address your question to a limited extent. Students in his freshman classes at his private school assume he is just one year younger. They have accepted him readily to the extent of including him at their table for lunch and willingness to work with him on math and science assignments. Lately he has begun hanging out with them after school also.
He has always fit in better with older kids than his age peers or even grade peers (he is slightly young for grade). His long-term best friend is 2 � years older and two grades ahead at our local public school. His local social/activity group consists of his 15-year-old sister�s friends who are mostly 3 years older and all sophomores at the public school. When she was dating a 17-year-old junior, ds and he went on a few outings pertaining to mutual interests and seemed very much like peers despite four years age difference. DS holds lengthy conversations via Facebook with a couple 19-21 year old college students (whom he has met IRL) and enjoys talking with his teachers during free time.
IMO, the more intelligent the individual or group, the less emphasis they place on proximal age when selecting friends. Therefore, if the school has smart students, the age difference might be less of an issue than if the students are average.
