ALBUQUERQUE, N.M. (AP) — New Mexico's two teacher unions want the state Public Education Department to slow its implementation of a new evaluation system for teachers and schools.

The National Education Association is considering legal action, while the American Federation of Teachers New Mexico is threatening to withdraw support for renewal of a waiver that allows the state more flexibility under the federal No Child Left Behind Act.

Patrick Sanchez, head of the National Education Association in Las Cruces, told the Albuquerque Journal that teachers have reached a boiling point over the department's plan.

"It's pretty fierce, close to nuclear," he said.

The system has provoked protests and talks of a teacher strike in Albuquerque as well as criticism from teachers and others around the state. Critics say the system places too much weight on student achievement and allows for classroom observations to be done by someone other than the school principal or assistant principal.

The American Federation of Teachers was among a group of lawmakers and teachers who filed a legal petition last month against the department, seeking to stop the system from being implemented for the first time this year.

The petition claims some elements of the administrative rule establishing the evaluations conflict with state law and are illegal.

On Friday, the NEA board passed a resolution authorizing its leadership team to look into legal action against the evaluations. A decision could come as soon as next week.

NEA New Mexico executive director Charles Bowyer said the union has worked with the department for several months to develop a collaborative process but hasn't seen the kind of openness it had hoped for.

Also on Friday, AFT New Mexico sent a letter to Education Secretary Hanna Skandera threatening to withdraw support for the No Child Left Behind waiver if certain conditions aren't met. Among other things, the union is demanding the state replace its A-F grading system for public schools and assure teachers they will get the support they need to meet Common Core standards.

The union also wants the department to apply for a waiver from the U.S. Department of Education that would allow New Mexico to delay for one year the new teacher evaluation system.

Larry Behrens, a spokesman for the state education department, said New Mexico students are better off now that they're not subject to the rigid approach called for by No Child Left Behind.

"We worked hard in a bipartisan manner with the Obama administration to be one of the first states to secure a waiver, and it's astonishing some want to return our children to that approach in the name of politics and defending the status quo," he said.

"We have great teachers and it's important to recognize them, and that's what the system does," he added.

New Mexico became the 11th state to receive a NCLB waiver in 2012. It allows the state to use the federally approved A-F grading system to rate schools based on student growth and other factors. No Child Left Behind focused solely on test scores and demanded that they improve a certain amount each year.