I wrote a memoir about my college years. I really think that the best audience would be young adults, but is there actually such a genre? Has anyone read any memoirs about kids/teens?
For whatever it is worth,
Farewell to Manzanar is in a paperback YA edition, and I believe has been treated as a YA title for quite some time. (It was originally published in 1973, I believe.) It is widely used in schools as a resource on the internment of Japanese-Americans during WW II.
You might want to examine the YA shelves at some big bookstores--look for memoirs there. Also, talk to some school librarians (middle school and high school) about your question. Public librarians might also be good resources.
Also, consider examining the last year's issues of
Publisher's Weekly to look for comparable books. Ditto,
School Library Journal, which should be the mother lode of relevant reviews. You should be able to track those down in libraries. That sort of information (take notes) will help in crafting queries and (especially) a book proposal.
--Ken