Fluffy Bunny Feet
Cosmic Mongoose
Where in character generation is it written at what TL your education was? Even if your planet doesn't operate at TL 15, does that necessarily mean that higher education does not cover TL15 stuff.
Frequently the benefit of more advanced technology is that it is easier to use, not harder.
Whatever world you originated on should have an education system compatible with its TL. Also there are pocket empires that are NOT TL 15 (and non OTU settings that may not be TL 15). Red Zone worlds that were never part of the Empire also wouldn't have that education level.
But even if you assume everyone has a TL 15 education what happens when you encounter that TL 25 Ancient device and need to try and figure it out?