What year did my brother in law graduate ?

He could have graduated between 2009-2011. Depends. My brother was born in 1992 and he graduated in 2010. September babies are weird with the schools in America. Sometimes, they push you forward or hold you back. My husband was born in September and was held back, so he was 18 when he started his senior year and graduated in 2002. He was born in '83. One of my good friends was born in October of '84, and she started with us, so she was always younger when she started.

Maybe in 2010..............

He never graduated.  He dropped out, joined the circus and travels the world getting shot out of a cannon while wearing shiny tights.

Probably 2011. 

It's impossible to say. Even if one were to assume he's from the United States and didn't fail or skip any grades but graduated on time as expected, two mighty big assumptions on an international website like this, one still wouldn't know because throughout the US the parents of a child born in September have the option of starting their child in kindergarten when their child is four or when their child is five.