Flames and billowing black smoke engulfed Yeshiva D'Rockland in Spring Valley.
Everyone made it out safely, but firefighters spent hours getting it under control.
The blaze started around noon. Witnesses speculate that it started in the kitchen.
The yeshiva sits just off Routes 59 and 45 and houses dozens of students, who spent the afternoon moving their belongings to other buildings.
Several fire departments responded, including Nanuet, Spring Valley, and Hillcrest.
One firefighter was treated for minor injuries.
The building houses a school in front, with a living quarters in the rear.