Executive functioning (EF) is found to be a powerful predictor for children's school readiness and long-term school outcomes. However, the current research base indicates that children with autism may have an increased likelihood of experiencing deficits in EF or delayed developmental trajectories. Additionally, although there is ample evidence that neurotypical (NT) children undergo a "sensitive period" with high plasticity in EF development in early childhood, and continue to make progress up to early adolescence, it is unclear if such a window of opportunity applies to autistic children in the same way it does for their NT peers, and if the longitudinal trajectory of growth follows a parallel pattern. Study 1 used the Early Childhood Longitudinal Studies-Kindergarten Class of 2011 (ECLS-K: 2011), and unconditional latent growth models were built for working memory and cognitive flexibility to identify the period of high plasticity in EF skills in autistic children and how it differed from that of their NT peers. It further investigated the relationship between autistic children's initial status in EF skills upon entering kindergarten and their rates of growth throughout their elementary school life. Lastly, it examined how the degree of heterogeneity in autistic children in their EF performances changed over time, and how such changes differed from that of their NT peers. Findings from Study 1 indicate that both autistic and NT children make steeper gains during the first few years of elementary school, and the rates of growth slow down as they get older. However, autistic children appear to have a wider window for high plasticity than their NT peers. Further, autistic children's lower initial status on working memory upon entering kindergarten predicted a higher rate of growth during the last three years of elementary school only, while a lower initial status on cognitive flexibility predicted a higher rate of growth throughout their elementary school years. Lastly, while both autistic and NT children show greater heterogeneity in their EF performances when they are younger, the heterogeneity decreases as they approach their "plateauing" points. However, the overall degrees of heterogeneity were higher in the autistic children than their NT peers, which indicates some degree of continued heterogeneity in their growth during the later years of elementary school. As indicated in Study 1, EF in autistic children is highly malleable throughout their childhood, and current literature base supports that various student-level and environmental factors play important roles in their development. In Study 2, conditional latent growth models were built to identify possible predictors for autistic children's working memory and cognitive flexibility performance upon entering kindergarten and their relative growth throughout their elementary school years. Findings indicate that socioeconomic status (SES) and students' approaches to learning (ATL) positively predicted autistic children's working memory performance upon entering kindergarten. Having ADHD, receipt of special education services at school, and students' ATL positively predicted autistic children's rate of growth in working memory during the first three years of their elementary school years, while student-teacher relationship (STR) predicted their rate of growth in working memory during the last three years of their elementary school. In addition, STR and ATL positively predicted autistic children's cognitive flexibility performance upon entering kindergarten, while living in a bilingual home environment positively predicted their rate of growth in cognitive flexibility during the first three years of autistic children's elementary school years. Implications and future directions are discussed