We investigate the hypothesis that Executive Functions (EFs) are implicated in the learning of science and mathematics by examining the relation between performance in two Science and Mathematics Conceptual Understanding and Conceptual Change (CU&C) tasks, and two Stroop-like Inhibition and Shifting EF tasks, in a group of 69 4th and 6th grader children. The results showed high correlations between accuracy performance in the CU&C and EF tasks even when Intelligence Ability (IA) and Age were partialed out. A path analytic model showed that performance in the CU&C tasks could be explained by performance in the EF and IA tasks, which were positively related to each other. Further analyses showed that accuracy of performance particularly in the CU&C tasks could be predicted by performance in the EF tasks, with high or medium EF scores being a prerequisite for placement in the group of high CU&C achievers.