Several studies have shown that the Simon effect, which is the advantage of spatial correspondence between stimulus and response locations when the stimulus location is task-irrelevant, decreases with increasing response times and is affected by preceding-trial correspondence. These modulations suggest the existence of control mechanisms that adapt our behavior to current goals by responding to the conflict experienced within a trial and by preventing the recurrence of a conflict in the subsequent trial. The aim of the present study was to assess whether these control mechanisms, which are well consolidated in adults and in children older than 8 years of age, are present in children between 6 and 8 years old. To this end, we tested 32 first-grade (6-7 years) and 34 second-grade (7-8 years) children on a Simon task in which correspondence sequence was manipulated on a trial-by-trial basis. The Simon effect was larger for first- than for second-graders and decreased with increasing response times only in second-graders. Crucially, for both groups, the effect was reduced when the preceding trial was noncorresponding, and the reductions were comparable for the two groups, indicating that trial-by-trial control mechanisms are already present in first-grade children and may be dissociated from within-trial control adjustments.