Do characters have to be typical to be realistic? Should they represent the majority of teenagers, or should they be the exception? The weird ones, the ones who seem to old for their bodies, too strong and too sure of themselves when they are supposed to be hormone driven crazies with no rational thoughts in their heads.
I believe my characters shouldn't be some stereotype adults dredge up to explain teenage behaviour, and since I am no longer a teenager I really have no idea what a 'typical' teenager would be like anyway. So my characters are just people, with real characteristics. Who looks back on their teenage years and thinks 'Yup, I was a typical teenager.' Every single one of us was at times a mess but we were also brilliant, passionate, caring, loved...and all of us showed flashes of the adult we were going to become.
People came back to me about one particular character and said he seemed a little too grounded for an 18 year old boy. All I can say is, I know from very personal experience that, though rare, young men like him do exist.