School pupils are using energy drinks to temper the effects of cannabis, a drugs and alcohol charity has said.
Swanswell said it has evidence of young people experiencing a "cycle" effect, drinking high-sugar drinks to counter the sedentary state that the Class B drug can cause, enabling them to "function" in their everyday lives.
Users then take cannabis to bring themselves back down from the high that the energy drinks create.
The NASUWT, the largest teachers' union in the UK, is working with Swanswell to lobby government to commission independent research into energy drink use and the long-term effects on health.
Findings from the analysis of the NASUWT's 2016 annual survey show 13% of the thousands of teachers who have responded cite the use of caffeine and energy drinks as a driver of poor pupil behaviour.
The NASUWT - meeting this weekend in Birmingham - has called for the introduction of national guidelines on recommended consumption levels of caffeine for children to help tackle pupil behaviour problems in schools.
Chris Keates, general secretary of the NASUWT, said: "For the last two years in our survey teachers have registered concern about the contribution of high energy drinks to poor pupil behaviour as a result of consuming excessive quantities of these drinks.
"These drinks are popular among young people who often think they are just another soft drink.
"Working with Swanswell, the NASUWT is pleased to be able to release initial guidance to start the process of awareness raising among parents, pupils and schools."
Debbie Bannigan, Swanswell chief executive, said: "Energy drinks can affect performance at school and lead to risky behaviour. We've even seen examples in our service of children taking cannabis to offset up to 800mg of caffeine a day."
She added: "Unlike other countries there's no official guidance on caffeine consumption for children in the UK.
"That's why we'd like the Government to commission independent research into the long-term health impact of energy drinks. This would enable them to publish evidence-based guidelines on the maximum amount of caffeine it's safe for children to drink."