Does aging stop in the Equestria Girls universe?

Been rewatching MLP, and when I got to the Equestria Girls movies my mind started hurting. The Mane six are hinted to be around young adult age (18-21) while Sunset was apparently Celestia's pupil before Twilight, and than the Dazzlings were apparently banished when StarSwirl was still alive and that was hundreds of years ago.

Yet, thier all highschool age somehow.

Does aging just not happen in the Equestria girls world and they all have set ages for eternity.....or did Habri not think of how it work beyond the amount of money they would make off of all the MLP human toys.

Something tells me it's the second one