In a rare appearance at a House Education Committee Wednesday, Madigan said the governor's plan would give unions too much control over the process of certifying teachers.
Gov. Rod Blagojevich wants to create a certification board with most of its members appointed by teachers unions.
The proposal is part of his plan to gut the State Board of Education, which currently has the final say on whether teachers are deemed qualified.
Supporters of the change say it would not be a major difference because teachers unions already have a big role in recommending who should sit on the certification board.