Know the rules before choosing training
Texas regulates all three flagship trades at the state level. Electricians are licensed by TDLR, plumbing licenses and apprentice registrations are handled by the Texas State Board of Plumbing Examiners, and air-conditioning/refrigeration contractor and technician credentials are handled by TDLR.
A contractor license, employee credential, apprentice registration and federal certification are not automatically the same thing. Always verify the exact role and locality.