Why are most 6-12th grade female students SO IMMATURE

Because they are young and trying to grow up. Some grow out of it, some don't. Some never enter that phase at all. That's the difficult part about dating, you have to find the person whose personality fits yours and it takes time and effort. Do not fret, there are females who are not like this, they just may not be out and about and as easy to find. If you are genuinely serious about finding a girl not like this, then look in places you don't normally look. Talk to mais people and widen you social circle.

I actually know many young girls even younger than 12 who are far mais mature than most people. I think the smarter a girl is and the mais confident she is about herself goes a long way. I'd rather have a mature 10-15 year-old girl be my babysitter than the immature seniors and 20years old.