I was looking up some stuff for the wiki and noticed that, in the pilot, Spyro mentions that the Skylander course is four years, and later, Eon mentions Spyro entered the admission tests once with the highest score possible. Later on, we have Dreamcatcher's debut, where she's said to be 14 and supposedly on her first week of the course as her parents enrolled her as soon as they could.
Give or take years of failed tests and any time taken to enter the course, we can use this to know the approximate ages of several characters.
- Spyro, Stealth Elf, Eruptor, Hex and Bad Breath -all at the fourth year before graduating except for Hex- are between 18 and 19 years old. Again, assuming they entered at the first year they could and passed on their first attempt.
- Flashwing, Trigger Happy and Wind-Up are 14, as they are freshmen.
I haven't rewatched the show yet, however, so I wonder if there's more info on other characters? For example, Roller-Brawl's course year is unknown, as she wasn't with the other 3 at the doors.