Thread:Paul.rea/@comment-69.114.23.36-20150204225345/@comment-4091815-20150205010134

It is as you stated "15 turning 16" - meaning that they're not all going the exact same age at the same time because not everyone has the same birthday.

Some Sophomores will be 16 throughout their sophomore year - others will younger or older depending on when their birthday falls.

Allison's is in February and Lydia's is in March - this automatically makes them older than 75% of the others born the same year.

Those are the only two birthdays portrayed on the show - despite that really badly researched calendar put out with the DVDs a couple years back - we don't actually have birth dates for the other characters.