Parents are demanding answers months after health issues started popping up at an Arlington junior high school, and they're no closer to finding a solution.

"We're losing teachers, the principal. Students are falling ill as well. It's a lot to deal with," said Delilah Perreira, PTA president for Nichols Junior High School.

Mysterious illnesses have plagued the school since September. Dozens of people who work at Nichols have gotten sick since then, some of them several times, with symptoms like headaches, nausea and dizziness.

It's become so bad that some teachers have taken to holding class outside.

Just this week, a staff member was transported to the hospital by ambulance. The school district doesn't know if that one is related, but until this is resolved, many Nichols parents are fearful of bringing their children to school.

Now, the school's principal is out and an interim leader has stepped in. The district isn't saying why she's gone, but it's raising a lot more questions.

"It's been the main focus of the school year," said Perreira. "That's all we talk about. It's all anyone is talking about."

It has been more than four months since Nichols had to be evacuated over health concerns. The illnesses continue but staff and students, like Perreira's eighth grade daughter Aaliyah, are no closer to knowing what's going on.

"I know some teachers have left the school and now have a permanent sub, and some teachers who used to get up and walk around, they really just sit there and say, 'Oh, my head hurts. I just don't feel good today,'" Aaliyah said.

The Tarrant County Health Department has interviewed about 60 staff members regarding ongoing symptoms. The principal is among them and now she's gone.

"I assume it's the health problems," Perreira said. "She has fallen ill multiple times over the last year, so I definitely assume it has to do with the air quality issue."

The district won't comment on personnel matters.

"She is out at this point and that's really all we can say," said Leslie Johnston, director of communications for the Arlington Independent School District.

But they do say they're doing everything they can to find a cause.

In a statement to NBC 5 late Thursday night, AISD Superintendent Dr. Marcelo Cavazos said, “The district continues to address concerns promptly and comprehensively and share information with staff and parents as it is received in order to resolve the situation and ensure the safety and health of our staff and students. We continue to work diligently to identify and address any possible conditions that may be causing the concerns reported by some staff members.”

So far, nothing has come back as a significant health threat. But while air quality and HVAC testing continues, parents like Perreira want everyone out of the school.

"It's been very hard," Perreira said. "I've thought about transferring her. But at the same time, I would feel like I'm leaving everyone hanging over there."

Her daughter has been tested for breathing problems, and she's seen classmates getting sick, too.

"They try to stay through the school day and then they just can't," Aaliyah said. "I'm scared that my friends and everybody else I know will get so sick, that they will have to be hospitalized."

A recent test of the HVAC system revealed some mold and something called "dirty sock syndrome," that's basically a bad smell. The district says it is resolving those issues, but says neither should cause the problems they're seeing.

They are waiting on one more big report and say if that identifies a serious problem, they may move the students out of the school.

Perreira is asking any Nichols parents who take their student in for a checkup to tell the doctor and the school what's happening, to keep better track of any student illnesses.

Parents had planned to speak out at a school board meeting Thursday night, but they did not sign up to address the board. The district continues to ask for patience as more tests are done.

"The health and safety of our students and staff is of the utmost importance,” said Board President Jamie Sullins. “The Board and district are committed to reviewing and addressing concerns to find a resolution to this issue. We are confident in the results of the testing and analysis done thus far that indicate nothing that would cause a health risk, and we will continue to work with industry experts to correct any potential issues in the building.”