I saw this film in my childhood. Some group of terrorist enter the school (boys' school i guess) and capture the school. the boss of the group has watch in which he will use that to trigger the bomb and explode the school in case if they lose control of the school. One of the captive student managed to change the chip (or some other electronic thing which control the trigger) in the watch and fixed it in one remote controlled toy plane. In the climax while fighting with the students the boss turn on the trigger to explode the whole school but the toy plane will start. This is the only sequence i remember about the movie. sorry for my bad english.
Toy Soldiers from 1991 with Sean Astin and Wil Wheaton about a group of rebellious boys fighting terrorists that took over their boarding school:
Billy Tepper is the leader of a group of rebellious boys at The Regis School. He has already been expelled from three prominent private schools. His best friend, Joey Trotta, is the son of the Head of the New York Mafia; Billy, all their friends and many other kids at the school have equally influential and prominent, if more law-abiding, parents. When Luis Cali's father is put in jail, he heads for the Regis School to put the son of the judge in charge of the case under hostage, only to find he has been removed. However, once he realises who the parents of the rest are, he decides the entire student body of the Regis School would be an even better bargaining chip.
They manage to switch the chip that triggers the terrorists' explosives with the one that's in a toy plane. Here's the trailer:
I'm pretty sure you're looking for Toy Soldiers (1991).
Never mind that none of the film's ordinary, easygoing schoolboys behave at all like the scions of prominent families, or that the long arm of coincidence gets a real workout during the course of the story. In fact, "Toy Soldiers" is a crisp, suspenseful thriller well tailored to the tastes of teen-age audiences, who will doubtless appreciate such touches as the equivalent microchips found in one student's radio-controlled airplane and the chief terrorist's detonator, which is rigged to blow up the entire school.
Could also be Masterminds 1997 with Patrick Stewart.
Trapped in a school which a gang of criminals has siezed control, a young troublemaker fights a cat and mouse battle from inside.
That was the first one that came to my mind. Good movie, if I remember right. I saw it once a long time ago.