http://pbskids.org/itsmylife/
It's My Life is a site for ages nine to 13, it's run by PBS and covers issues such as puberty, the effects of drugs and alcohol on the body, advice about friendships and family issues, ect. It's like Scarleteteen's younger cousin.
Unfortunately it hasn't updated since 2013 due to loss in funding so you can't submit questions and / or post on the message boards but the blog posts, articles , and games are still up.
http://kidshealth.org/
Kidshealth.org was created by a a nonprofit pediatric health organization and has resources for all ages.
https://www.girlshealth.gov/
Girlshealth.gov was created by the U.S. department of women's health and is primarily targeted at teenagers but has useful resources for pre-teens as well.
I hope this helps!
