It is a scientific fact, tested and proven by generations of pupils, that experiments in school laboratories win young people to the cause of science. White coats, goggles and the chance to set fire to things foster a passion for chemistry that even years of examinations do not extinguish.

But government advisers and eminent scientists are warning of a disturbing development that could endanger generations of future scientists: pupils are no longer allowed to experiment.

Health and safety concerns are preventing students — including those taking A levels — from performing vital and exciting investigations into what happens when one sets fire to magnesium ribbon, or drops a small glob of sodium into a dish of water.

The fear of burns, spillages and volatile reactions means that even mundane procedures such as distillation are often viewed online rather than performed in the laboratory. Professor John Holman, the Government’s chief adviser on science in schools, and Professor David Phillips, incoming president of the Royal Society of Chemistry, told The Times that it was vital for pupils to learn how to handle hazardous substances and to experiment.

Professor Holman, who is also director of the National Science Learning Centre, said trainee teachers spent too little time preparing exciting practicals. “There is much less practical work now because of a huge focus on exams,” he said. “Schools are so aware of health and safety — they will say, ‘That’s too dangerous’.

“But in most cases you can do it, you just need to take precautions. The schools do formulaic investigations which give pupils a higher grade.”

Professor Phillips, who is also Emeritus Professor at Imperial College London, said: “Many of the experiments we did handling strong acids wouldn’t be allowed today, but learning to handle dangerous materials teaches you how to deal with things sensibly,” he said. Without the stimulation produced by making elements combust and fizz, pupils would not continue science beyond GCSEs, the professors warned.

“All the evidence points to practical work being the thing that pupils like to do,” Professor Holman said. “This isn’t about how do you get more Grade Cs in GCSEs, it’s about how you inspire more young people.”

The comments follow an Ofsted report warning that the national curriculum and testing regime led to boring science lessons. Schools spent too much time drilling students for tests, it said.

Jane Lees, head of Hindley High School in Wigan, and a former head of science, agreed that health and safety had put an end to a number of “whiz-bang” experiments. “But we’re moving on to different ways of teaching science — with videos, and on the web with virtual learning environments which are quite as interesting. It’s a different way of learning but it should still be able to turn them on. What you need is inspirational teachers.”

Experiments at risk

Ammonium dichromate volcano Make a pile of ammonium dichromate and set the tip alight using a magnesium fuse. The result is a tiny volcano, complete with ash, steam and nitrogen gas

The thermite reaction Mix metal powder with metal-oxide to create thermite and set it alight. The mix will burn at an exceptionally high temperature

Potassium in water The classic school experiment. Drop potassium into water and it reacts violently, making hydrogen, which then ignites in a small fireball

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