Ahead of a high-profile summit aimed at helping the State Education Department finalize a new teacher evaluation system, Chancellor Merryl Tisch said she hoped the marathon event would lead to consensus.

“It’s time for everyone to stop yelling and casting aspersions,” Tisch said in an interview Wednesday.

“This has been so highly politicized and charged that sometimes it’s very difficult to have voices of reason be pervasive,” Tisch added. “We’d like to be a voice of reason.”

The event was made necessary by a law, passed last month, that will make sweeping changes to the state’s teacher evaluation system. That law ensures that state test scores will count for more of a teacher’s final rating, and requires teachers to be observed by an outside evaluator. Other details of the plan were left up to officials at the State Education Department, and the law requires the department to gather feedback from teachers, principals, and parents, as well as from education experts and researchers, as they make those decisions.

The event (which is invitation-only but can be viewed live online here) will provide state  officials with plenty of opinions. Accomplishing Tisch’s goal appears less likely, given the sharp ideological divides about the purpose of a teacher evaluation system and the  need for an overhaul — debates that have filled New York legislative chambers for  years — and a law that leaves officials without much flexibility.

By the time the eight-hour summit is over, the state’s 17-member education policymaking board will have heard from more than 30 people, representing nearly as many organizations, broken out into seven separate panels. If that’s not enough, the Regents could also pore over more than 600 pages worth of research, op-eds, and rebuttals to op-eds that have been posted to the department’s website in recent days.

Whether there will be much use for that feedback is also debatable. Especially when it comes to how student performance will be measured, the law is clear that state test scores must be the sole measure, and that those results will count for half of a teacher’s rating, though Tisch has said the 50 percent figure is just one interpretation.

Powerful education advocacy organizations say the event remains a chance to influence a debate that has only become more important, three years after a new evaluation system was introduced throughout New York (except New York City, which adopted a new evaluation system in 2012).

Robert Lowry, who will testify on behalf of the state’s school superintendents, said the new law was “incredibly flawed, and there’s a great risk of making the evaluation system worse.”

Lowry said he believed there were two main areas in which state officials could improve the evaluation system. First, the state could guarantee that a principal’s observations of a teacher count for more than those of an independent evaluator, he said. Nearly 70 percent of superintendents statewide said the principal observation process was having a positive impact on improving teacher quality, according to a survey conducted last summer.

Chancellor Carmen Fariña has echoed that point repeatedly, saying outside observers would not only be a burden on the city but also a unhelpful to teachers.

Second, Lowry said that he hoped the department would figure out a way to give districts more time to introduce the new evaluations. The state law requires districts to negotiate a plan with their local unions by Nov. 15, and Lowry said the deadline, which is tied to a state funding increase, could complicate negotiations.

If the state can’t extend the deadline, officials should develop a “default” evaluation system for districts that can’t negotiate their own plans, Lowry said, a proposal that the association representing the state’s school boards said it would also support.

The event comes just days after a bipartisan education bill was introduced by Assemblywoman Catherine Nolan and Senator John Flanagan, who chair the education committees in their respective houses. The proposed law, which features changes to state testing and Regents appointment policies, would extend the implementation deadline by a month, from Nov. 15 to Dec. 15, and reaffirm that certain demographic information would be included in the complicated formulas that the state uses to calculate student growth for teacher evaluations.

United Federation of Teachers President Michael Mulgrew will be appearing at the event as well. The city teachers union wants the state to do away with any measurements of student learning that rate teachers of non-tested subjects, such as art and physical education, based on test scores of students they don’t teach.

Tisch said she expects the role of the independent evaluator to receive a lot of scrutiny Thursday, noting that they will be a costly logistical headache for districts. Ultimately, Tisch said, she is looking for proposals that are not too extreme.

“It’s the porridge scenario,” Tisch said. “Is it too hot, is it too cold or is it just right?”