Can anyone in America explain your school system to me?

Hey guys, i'm planning on writing a a new story and it involves school, but because i'm from the UK and i'm basing my story in America I can't write in detail about school days because i have no idea what school is like over there!

If you'd be kind enough to comment i'd need to know what agges you left high school, at what ages are you a Freshman, Sophomore, Junior and Senior, what you're school time tables are like and what sort of lessons you have.

I'd love you guys forever and ever (:
Lots of love, Charlie.
<3
xx