At School

There was a school. In the middle of class the fire alarm went off. Fire trucks were outside. But everyone could stay in their class. Why was that?

Answer: The fire was outside. HA! Source: https://riddles.com/index.php/4122

There was a school. In the middle of class the fire alarm went off. Fire trucks were outside. But everyone could stay in their class. Why was that? — At School by Purplehartz12 Riddle