In Ireland, dyslexic students can apply for reasonable accommodations in Leaving Certificate examinations. One such accommodation is the Spelling and Grammar Waiver (SGW). Questions have been raised regarding its validity, and it has been suggested that it gives an unfair advantage. Mock Leaving Certificate English paper scripts were collected from 31 dyslexic students who had been granted an SGW and 31 nondyslexic students who had not been granted any accommodations. All scripts were marked twice, eight weeks apart, by the same marker, once in the standard fashion and once with an SGW. Dyslexic students' scripts marked with an SGW had a significantly higher mean score than when marked in the standard way, and it was similar to the mean unaccommodated score of nondyslexic students. However, nondyslexic students also received a similar boost in scores when accommodated. Two-way repeated measures ANOVA showed no "differential boost" for the dyslexic group, but a significant boost for both groups when accommodated. Results suggest that the SGW is not a valid accommodation but confers an advantage to those that have it. This study needs replication using larger numbers, with real Leaving Certificate scripts and examiners, and the reasons for the increase in scores also need investigation.