AVONDALE, Ariz. -- There is new outrage from parents and school board members about a mercury spill at Agua Fria High School -- they want to know why administrators went back on their word.

• Watch: Teacher Involved In Mercury Spill Giving Science Lessons

In a letter to a teacher involved with the spill, Agua Fria Superintendent Dudley Butts said a teacher involved with the spill would be reassigned as a substitute. The letter said the "assignment as a substitute teacher would not include any science class openings throughout the district."

Agua Fria Assistant Superintendent Lexi Cunningham recently assigned that teacher as a permanent substitute for science classes at Desert Edge High School.

Before an Agua Fria school board meeting Wednesday night, Butts and Cunningham refused to explain why they reversed their decision.

"I'm just not going to answer any personnel questions no matter how many times you ask them and that's how it's going to be," Butts said.

Butts and Cunningham also refused to explain how the Feb. 12 mercury spill happened at the high school.

CBS 5 News has been trying to get answers to basic questions about the spill.

They include, "Did teachers handle the mercury?" and "how much will it cost to clean up?"

When asked when answers would be available, Cunningham said, "As long as our investigation takes."

Agua Fria board member O.K. Fulton said the teacher involved with the spill should not be teaching science.

"I would not be okay with that," Fulton said.

"It's going to endanger students on one campus, what's the chance of it happening somewhere else. It looks badly," he said.

Outside Desert Edge High Wednesday afternoon, parents learned about the science teacher's placement from us.

"I don't think that's a good decision. I think we should have been made aware of that," said Craig Williams.

Judy Famolaro said she plans to call district officials about the teacher.

"I'm frustrated as a parent because I don't want my child or any of the students being impacted the way they were at Agua Fria," she said.

The Feb. 12 spill shut down Agua Fria High School for three days. The school board voted against adding those days back onto the school year Wednesday night.

Officials said the cost of the 11-day clean up of mercury at the school will be expensive, and so far, the bill is at least $150,000.

However, they are still waiting for several bills from the companies that conducted the clean-up.