Figures obtained by the Welsh Conservatives show that the number of dyslexic pupils in Wales obtaining a â€œgoodâ€� GCSE in core subjects is falling.
In 2017, 76.2% of pupils with no special educational needs (SEN) achieved an A*-C grade in English, compared to 40.2% of 723 dyslexic candidates.
In maths, the figures were 69.9%, 20.2% more than their dyslexic counterparts. The figures for science were 84.5% versus 74%.
The attainment gap for English in 2015 and 2016 was 33.1% and 35.9%, respectively. In maths, the divide was 24.2% and 32.2% in each of these years.
A greater proportion of dyslexic students achieved a good GCSE in science in 2015, but the trend reversed in the following year.
The news follows concerns expressed by the Childrenâ€™s Commissioner for Wales, Sally Holland, who warned that children and young people with learning difficulties are not getting the support they need.
Shadow Cabinet Secretary for Education, Darren Millar, said:
â€œThe attainment gap between those pupils with learning difficulties and those without is unacceptable.
â€œChildren with dyslexia should be given the support they need to flourish and reach their full potential, yet these figures suggest that this is far from the case.
â€œThe Welsh Government must develop a clear action plan to address the challenges faced by young people with dyslexia to ensure that schools and pupils get the help that they need.â€�