The BBC the number of pupils being taken out of school to be taught at home has doubled in four years – with many of them believed to be autistic.
Some 1,906 pupils were removed in 2016-17, up from 864 in 2013-14, according to council data.
National Autistic Society Cymru said many were autistic children who were struggling to cope in school.
Children’s Commissioner for Wales, Sally Holland, said she was concerned some schools wanted autistic children removed to improve their results.
The council figures – received by BBC Wales by all but one council following a freedom of information request – found the highest number of pupils leaving school to be home educated was among older secondary school pupils.
In 2016-17 there were 332 children aged 15 taken out of school, compared to 156 children aged 11.
Meleri Thomas, from the National Autistic Society Cymru, said the school environment often proved too challenging for some autistic children.
She said: “Some parents have told me they have been encouraged to home educate because their child might be affecting the school or local authority’s performance data around exam results or attendance figures,” she added.
Read more Autism concern over home schooling rise
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