A Montgomery County’s teachers union may be preparing to fight the Maryland State Department of Education regarding the department’s new requirements for teacher evaluations.

Montgomery County Public Schools leaders heard from the state department earlier this month that, starting next year, the system must use students’ results on state tests to determine 20 percent of a teacher’s effectiveness.

The Montgomery County Education Association is now trying to determine just how much power the state has to impose changes on local systems, Tom Israel, executive director of union, said Thursday.

“The question is, do they have the legal authority to impose something on local districts?” Israel said.

Montgomery is set on keeping its evaluation system, which is a component of a Professional Growth System that school and union leaders say has become a proven, national model.

Israel said both the school system and the union have been “fairly clear” that they will not use Maryland State Assessments to judge teachers, stating that it would compromise their system.

Union leaders are trying to determine next steps by talking to not only the state’s Education Department, but also the U.S. Department of Education and Gov. Martin O’Malley’s office, Israel said.

Christopher S. Barclay, president of the Montgomery County Board of Education, said that Israel’s comment about how the system will not comply “is not helpful.”

“I look forward to working with MSDE to get this resolved in a way that is amicable and does not compromise our professional growth system,” Barclay said.

Montgomery has been told it has until May 15 to resubmit its plan.

When asked what possible punishment Montgomery could face if it does not comply with the state’s requirements, Bill Reinhard, MSDE spokesman, said the department is “not really looking at possible sanctions at this point.”

But David Volrath, who leads teacher and principal evaluations for the department, along with Doug Prouty, president of the teachers union, both said previously that the state could withhold funding.

The state supplied 27.2 percent of Montgomery County Public Schools’ $2.2 billion budget this year.

Prouty added that Superintendent Joshua P. Starr could be put in jail, adding that was unlikely.

No one really knows at this point, said Sen. Nancy King (D-Montgomery Village), who on Thursday heard from State Superintendent Lillian M. Lowery at a state Senate Budget and Taxation subcommittee meeting in the General Assembly.

King and others asked Lowery to provide more details about why Montgomery and eight other systems in Maryland had their evaluation proposals rejected.

King said Lowery focused on the 20 percent — not the other components of the evaluations.

King said she has “heard rumors” of what consequences local systems will face if not complying but does not know for sure.

Israel and other union and school system leaders in Montgomery say the Maryland State Assessments are outdated — they will be replaced with new state tests in the next few years — and unreliable, not showing an accurate picture of how much a student has learned.

Montgomery’s evaluation model states that student growth, including student projects, in-class tests and course work, and more, will be a “significant” part of the teacher’s evaluation. But the state said the system needs to show that it is compatible with the state’s model, in which student work determines 50 percent of a teacher’s effectiveness.

This means that the state is requiring Montgomery to go by the same rules as the 22 local systems that signed onto federal reform program Race to the Top, which promised states and local systems money for agreeing to certain measures, some of which are meant to improve teacher effectiveness. Frederick County Public Schools was the only other system in Maryland not to sign on.

Volrath said that even though the systems cannot be held to Race to the Top requirements, they are still held to requirements for teacher evaluations listed in state law and the state’s waiver for No Child Left Behind. Israel said the system believes its current system is in compliance.

“We have no intention of abandoning a high-performing system for one that is untried and untested,” Israel said.