Paul Peterson says that it was not Al Shanker who first advocated the charter school concept more than 20 years ago. Roy Budde came up with the original concept and Al Shanker spoke about it, but his view was very limited. Joe Nathan and Ted Kolderie championed greater autonomy and for others outside of education to have the opportunity to start new charter schools. Most significantly, the Nathan/Kolderie model of charter schools proposed teachers operating outside of collective bargaining agreements established in school districts.
Al Shanker, leader of the New York City's United Federation of Teachers, couldn't tolerate the idea that charter schools would operate with anything other than union teachers at the helm. And thus it remains today, proponents of teacher's unions oppose charter schools.