A cleaner at Kenmore West High School was fired last week after he was accused of being in a locker room while eighth-grade girls were using it.
His union says the school district never gave him the chance to rebut those allegations. It plans to file a grievance.
"It's a very serious thing to charge someone without performing all the necessary steps to make sure those accusations are true," said Peter Elinski, president of the Kenmore-Tonawanda School Employees Association.
Superintendent Steven A. Achramovitch said the district followed due process and acted responsibly.
"From the district's perspective, this was a very serious allegation we investigated," he said.
A community swim league used the high school pool Sept. 29. Achramovitch said school officials learned the evening of Oct. 1 that a man was seen in the office of the girls locker room Sept. 29.
District officials called the cleaner in for a meeting Oct. 4 and placed him on administrative leave, they said.
"As soon as we got the official word as to what was taking place, we started putting the pieces together, trying to contact individual parents that were there, getting statements from individuals that were there," Achramovitch said.
The district reported the incident to Town of Tonawanda police but did not ask police to get involved.
District officials held an informal hearing Oct. 15 and presented the information they had, Achramovitch said.
Elinski said the employee was not given a copy of the police report or any information about the accuser.
The superintendent said the union had been given at least two days' notice, which was enough time to collect whatever information it needed.
The cleaner was given the chance to resign, which he declined, union officials said.
The employee and his union representatives say the next they heard from the district was at 7:45 a.m. Friday, when school officials asked them to talk to the School Board in 45 minutes, at 8:30.
Union officials said they were not given enough notice of the meeting. Achramovitch said the district tried unsuccessfully to contact the employee the night before.