School record data including repeating, IQ score and last regular school grade completed were collected on 51 male and 65 female adult schizophrenics, their siblings and age mates. The school performance of male schizophrenics was inferior to female schizophrenics on all three measures. The male probands but not the female probands did significantly more poorly in school than their age mates. There was a sizeable group of low-IQ males, but not low-IQ females, who received a diagnosis of schizophrenia in a state hospital setting. The within-family results indicated that the pre-schizophrenic differed consistently on school performance from both his siblings and age mates only when the schizophrenic-to-be was a boy who belonged to a low-IQ sibship. The significance of these results in understanding the relationship among schizophrenic illness, sex and IQ level is examined.