A bill introduced in the state Assembly could force Chancellor Joel Klein to spend a quarter of new state school funds won in the Campaign for Fiscal Equity lawsuit on lowering class size.

Called the “Class Size Reduction Act,” the bill transported an ongoing spat between Mr. Klein and the teachers union president, Randi Weingarten, to Albany, where both were testifying yesterday on Governor Spitzer’s budget proposal. Mr. Klein has often said that improving teaching should take precedence over reducing class size, while Ms. Weingarten is an avid supporter of smaller classes.

In his budget, Mr. Spitzer proposed increasing New York City’s state aid by $3 billion a year within four years and suggested lowering class size as a way for school districts to fulfill their “Contract for Excellence,” the accountability mechanism he proposed. He did not make lessening class size a requirement.

The bill’s sponsor, Assemblyman Rory Lancman of Queens, said he had more than 50 Assembly supporters of the bill so far, including Assemblywoman Catherine Nolan, the new chairwoman of the Education Committee. He said he anticipated that a Senate version would be introduced this week.

In her prepared testimony for the Legislature’s joint Ways and Means and Finance committees, Ms. Weingarten, who Mr. Lancman said had worked with him on the bill, urged lawmakers to vote for it, reviving her longstanding criticism of the chancellor’s stance on class size.

“Some districts may give lip service to the goal of reducing class size, as Chancellor Klein does, but not really accomplish much,” she said.

When questioned by lawmakers at the hearing, Mr. Klein defended the city’s efforts to decrease class size, his spokeswoman, Melody Meyer, said. He said 60% of the city ‘s empowerment schools, where principals are given great discretion over their budgets, had chosen to spend money on adding new teachers.

During the hearing, lawmakers also questioned Mr. Klein’s plans to restructure the school system by expanding the empowerment model and adding two new school support structures next year that will include an increased role for private groups. Parents, teachers, and city lawmakers have called on the chancellor to halt his plans and listen to their concerns, including fears that for-profit private groups have increased their influence over the school system. Today, they are planning a protest rally in Midtown.

“It’s not acceptable that each individual school … can choose whether or not to employ the most effective tactic we know to achieving education excellence,” Mr. Lancman said. “Parents and teachers are tired of the city giving them the runaround and doing everything but lowering class size.”

He said his bill was modeled on a proposal created by parents and teachers as a New York City ballot referendum. The mayor blocked the referendum, arguing that class size was a state matter because it involved state funds, Mr. Lancman said.