“The red bellies really like to hide in dark places so that bag, the inside lining was black and dark so that is where they feel most protected,” she said.

“It was a bit disorientated and a bit out of its comfort zone in and around the bag and so it must have felt secure in the dark bag.

“The red bellies eat lizards and frogs and so I wouldn’t be surprised if there are probably lizards around the area where the kids keep their bags and the gardens nearby."

Ms Field said a creek running down the back of the school and a rock retaining wall out the front created the “perfect habitat” for red-bellied black snakes.

“It is not the first time I have been to that school and they are very proactive about minimising what they can in terms of habitats for snakes,” she said.

“They mention it to the kids quite often to be snake aware and are also on top of their first aid requirements.

“There is nothing they can do about the creek or the rock retaining wall so they know they are going to be there, they are just smart about it.”

Ms Field said while no-one has ever died from a red-bellied black snake bite in Australia, you could get a “nasty infection” and be “in a lot of pain” from their venom.

“They are really reluctant to bite and they are one of the most gentlest venomous snakes that we handle,” she said.

Snake Catchers Brisbane, Ipswich, Logan & Gold Coast shared an image of the snake in the girl's Harry Potter-themed backpack to Facebook on Tuesday, which attracted a few jokes about it being a “Slytherin prank” and better than a “Vegemite sandwich and a bruised apple”.