Would matter a lot.
Could be government academies and secret, criminal underground groups.
Could be specialist orders or the like.
Could be special private schools, perhaps with charity scholarships (Perhaps not! Requiring education the poor people can't afford is a classic way to keep them down.)
Much depends on exactly how hard it is. Not to mention what powers you can train into -- superstrength? telekinesis? superspeed? flight? energy attacks? green thumb? healing powers? -- and how powerful they are. A government would be happiest with none, but then second best, with many to pit against each other (except how much damage does that do?).