Mobile phones should be banned from the classroom because they are detrimental to school results, the education ministry has said.

“Scatterbrained” children, unable to withstand the lure of their phones, score an average of 1 to 1.5 points lower in tests, research has found.

The new rule, which will become effective from January 1 next year, will apply to secondary schools but not MBO trade schools and HBO colleges. A decision about primary schools is expected on Wednesday.

Exceptions will be made for pupils who need a phone, tablet or smartphone for medical reasons or if the devices are used for educational purposes.

School and parents’ organisations and teachers and pupils unions have all signed up to what is currently a guideline. If unsuccessful, it may become law, minister Robbert Dijkgraaf said.

Schools said they welcome the measure which is putting an end to what has been a long political wrangle about the desirability of government intervention in school matters. Schools will still be free to shape their own general policies around mobile phone use, Dijkgraaf said.

A third of schools have already adapted their policies to conform with the new guideline, Henk Hagoort of secondary schools council VO-raad said. “No one wants unnecessary distractions in class and that is why they should only be used if relevant to the teaching process,” he told broadcaster NOS.

Parents’ organisation Ouders & Onderwijs said the collective agreement is a great help for parents who forbid their children to use their phones in class. “It’s difficult to be the lone voice of disapproval and say ‘you can’t have your phone even if your friends can’,”  director Lobke Vlaming told the broadcaster.

Teachers could not be happier, spokesman Jelmer Evers of teachers union AOb said. “We have never had a quicker response to a survey. A whopping 73% of our members in secondary education said they wanted a national ban on mobiles in the classroom,” he said.

Pupils union LAKS said they had signed up to the agreement because phones can be a problem in lessons. “Phones are part of pupils’ lives but we can see that they are a distraction in class,” LAKS chair Rafke Hagenaars said.