If you have at least 4 Lessons in play, your Spell cards with a printed Power cost of 6 or more need 2 less Power to play. (You still need at least 1 Power that matches.)

'(Order of Merlin, First Class, Grand Sorc., Chf. Warlock, Supreme Mugwump, International Confed. of Wizards)' — Hogwarts letterhead