Academic attainment in children with Autism Spectrum Disorder (ASD) is under-studied, with associated factors largely undetermined. Parent-reported attention symptoms, attentional-switching and sustained-attention tasks were examined to determine relationships with mathematics and reading attainment in 124 children aged 7–12 years; sixty-four with high-functioning ASD, half girls, and sixty age- and gender-matched typical children (TYP). With full-scale IQ controlled there were no differences in mathematics, reading, attentional switching or sustained attention. In regression analysis, attentional switching was related to mathematics achievement in ASD but not TYP children. Findings highlight attentional switching difficulties are linked with poorer mathematics outcomes in ASD.