It started around 3 a.m. inside the second floor of the Hebrew Academy of Five Towns and Rockaway on Washington Avenue in Lawrence.
"It was confined to one classroom, a large classroom," Lawrence-Cedarhurst Fire Department Chief Edward Kohler said. "A little extension to the hallway and a little extension to the outside of the building when the flames came out the windows."
Firefighters reported heavy smoke throughout the building.
"It was a textbook operation," Kohler said. "The members did a really good job. They had smoke. They had to find the fire. There was a lot of hose stretching through hallways upstairs and ultimately to the classroom that was on fire."
Fortunately, no one was injured.
Firefighters later determined that power strips in the computer server room caught fire. Officials have ruled the fire accidental.
Damage was limited to the server room and the adjacent classroom.
There will be no school for students of the lower school Thursday.
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