Avengers heroes Thor, Iron Man, Black Widow, Captain America and the Hulk are used to saving the planet in epic showdowns but now they face the ultimate challenge: keeping a classroom full of teenagers quiet.

The latest Marvel film Avengers: Endgame - which is breaking box office records - is now being used by teachers as a tool to maintain discipline, with the threat of plot giveaways used to keep pupils under control and on task.

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The behaviour-management technique came to light when a US teenager posted a picture online of the classroom whiteboard.

The photo shows information gradually being filled in about the action that takes place in the first 20 minutes of the film and is accompanied by the comment: “My teacher was filling in Endgame spoilers every time the class got too loud”.

The post, in a chatroom on the Reddit website “dedicated to Marvel Studios and the Marvel Cinematic Universe as a whole!”, attracted 122 comments. Some contributors saw the amusing side, with one commenting: “That’s diabolic, as well as funny.”

Others were, however, less impressed; one commented: “That’s not fair, the kids who don’t care can ruin it for those who do...”

The discipline technique was also picked up by Scottish computing teacher Kate Farrell, who posted a Tweet with her reaction.

She described the behaviour management strategy as “ingenious” but also expressed some sympathy for the Marvel fans in the class.

She said: “This is such an ingenious behaviour management strategy! ...but a bit mean ;-) Also, there will be kids who don’t give a damn about Marvel who will be deliberately loud to spoil it for others :-(“