This follow-up study aimed to examine (a) the impact of 4.5 years participation in postsecondary education (PSE) on students with intellectual disability (ID) compared to adults with ID who did not participate in PSE, (b) whether a different impact on crystallized and fluid intelligence after 4.5 years would be found among PSE students with higher and lower initial IQ, (c) micro-level individual differences in each PSE group. The WAIS-III was administered at Time 1 and after 4.5 years to PSE students in an inclusive full requirements model (n = 6; IQ = 66-72) and to the PSE students in the inclusive adapted requirements model (n = 6; IQ = 54 -61) and adults with ID who did not participate in the PSE (n = 12). Only PSE students showed improvement in FSIQ, verbal and performance IQ in this Time 2 evaluation, with individual differences between the students. FSIQ and verbal IQ of students with a higher IQ exceeded the diagnostic cutoff of ID (IQ < 70-75). Despite the small sample size, the findings indicate that time extension and mediation strategies enable adults with mild ID to achieve academic goals, thus, supporting the Compensation Age and the Mastery Learning theories.