The number of pupils in England given 25% extra time in GCSEs and A-level exams because of a special need has almost doubled over five years.
There have been warnings about schools gaming the system - but the latest figures show the numbers getting allowances in exams continuing to rise.
The exam watchdog, Ofqual, says it will contact schools with unusually high levels of pupils receiving extra time.
Exam boards say they have "robust procedures" in place. They have tightened regulations and require evidence of pupils' need.
Ofqual figures show 223,000 candidates were given 25% extra time to sit exam papers in 2016-17, up by:
- 8% on 2015-16
- 36% on 2013-14
In total, more than 390,000 exam candidates were given extra allowances because of physical, social, mental or emotional needs.
There was an increase in pupils needing modifications to their exam papers - such as using different coloured paper.
But the number of students using exam papers in Braille fell to 1,130.
Ofqual said it was fair for pupils with disabilities to receive a "reasonable adjustment" when taking exams but some schools were much more likely to have high numbers of pupils receiving extra help and if there were no "obvious good reasons" it would now ask them to "review their approach".
But it would also contact schools where unusually few pupils received extra help, in case there were candidates missing out.
A report earlier this year suggested independent schools were disproportionately likely to have pupils receiving extra time in exams, but the Ofqual figures do not have a breakdown of state and private schools.
