The purpose of this experiment was to examine the development of motor preparation across three groups of children aged 6, 8 and 10 years old. The foreperiod duration (500, 1000, 2000 and 4000 ms) and the motor preparation conditions were manipulated using a priming procedure. Two type of primes were provided: (1), a prime carrying no advanced information (neutral condition); and (2), a prime giving advanced information on the nature of the motor response to execute, allowing the participant to prepare for it (selective condition). Reaction time and response errors were analyzed. Results showed that under both conditions, the optimal motor preparation was reached within the same time frame which decreased as age increased. As to the optimal alertness level (neutral preparation), it is maintained longer as age increases, whereas the optimal motor programming level (selective preparation) is reached only for specific foreperiod duration.