The Dyslexia Foundation is appalled by the small number of children with disabilities from low decile schools who received help with last year's NCEA exams.
Last year, government agencies made it cheaper and easier for students at low-decile schools to apply for extra assistance such as additional time or having a reader-writer.
But the Foundation's chairperson Guy Pope-Mayell said figures provided under the Official Information Act showed many children were still missing out.
"Unfortunately the latest data still shows that it's 17 times more likely that a student in a decile one school will get SAC (special assessment conditions) compared to a high decile school. And we find that to be an appalling outcome from the effort that was to be made over the last 12 months."
Mr Pope-Mayell said low-decile schools needed more help to assess students and apply for special assessment conditions.
The Qualifications Authority said it has been working with the Education Ministry to raise awareness of how to apply for the special conditions.