User blog comment:Paul.rea/Teen Wolf News 081314/@comment-76.20.116.61-20140830213631/@comment-4091815-20140830220231

As long as they are consistent within their own timeline the continuity is fine.

The average age of a High School Junior in the US is 16-17.

Lydia will turn 18 in March near the END of her Junior year. This is well within real world parameters.

Again, as long as they don't suddenly change her age, its not a problem.