Adderall is approved for use in children 6 years and older. The dose is usually based partly on weight and partly on symptoms. There are full-grown adults who take only a 10 or 20 mg per day dose, and there are children who take more than 30 mg per day. The dose should be determined by the doctor. If you are concerned about your child's dose, ask the doctor to explain how he or she determined the appropriate dose. Always monitor your child for possible adverse effects of the medication, and report these to the doctor.
Best of luck,
Casey