Okay, I was doing my app for Sengoku Legends, and was thinking how much I HATE proportions. So I decided to make myself (and all you wonderful people out there) a little.... Reference! I compared the heights to charas in Ouran High School Host Club, because it's an anime/manga I, and others know well (I will put references to other anime/manga out there as well later on). Each circle is about the size of a head that way it's easier to make proper proportions. The petite (or loli/shota character) height is roughly the height oh 6 heads, the average/cute (or short but not midget-ish) height is 7 and so on.
Those are in bases of highschool to adult, if you are doing elementary school kids, I recommend the petite height, middle schoolers between 6 and 7 (find some mix there-of that you like).
I'd add another "head" for every 6 or so in.
Petite (around 4' 6'' to 4'11''): Mitskuni Haninozuka (Ouran High School Host Club) Taiga Aisaka (Toradora) Tōshirō Hitsugaya (Bleach)
Average (Cute) (around 5'1' to 5'5''): Haruhi Fujioka (Ouran High School Host Club) Haruhi Suzumiya (The Melancholy of Haruhi Suzumiya) Mizuho Asano (Bleach)
Average (around 5'6'' to 5'9''): Ryūji Takasu (Toradora) Hitachiin Brothers, Kaoru and Hikaru (Ouran High School Host Club) Kyon (The Melancholy of Haruhi Suzumiya)
Tall (around 5'11'' or so up): Takashi Morinozuka (Ouran High School Host Club) Ichigo Kurosaki (Bleach) Gin Ichimaru (Bleach)
(I apologize for the confusing Category.... I didn't know what to put this in -.-')