A ferocious wild monitor lizard rampaged through a school and terrorised children in Thailand.

The aggressive reptile was found resting on top of a tree in a school in Kamphaeng Phet province on November 22.

Concerned school staff climbed up the tree to scare the creature down but it only went up higher.

However, the 20kg lizard slammed onto the school’s roof when the tree’s branches broke under its weight while it was trying to escape.

The startled creature then hopped down to the ground before running into a first-grade student classroom to hide.

Scary video shows the school children screaming in fear after seeing the giant lizard entering the class and hiding under a still-occupied wooden chair.

Unlike his terrified classmates, one boy hilariously remained unfazed as the large reptile scuttled under his seat.

The lizard was eventually caught by the school staff and later released into the wild unharmed.

Onlooker Somyot said: ‘We believe the dogs must have chased the lizard up the tree. Luckily, we caught it before it could cause more chaos in school.’