Focalin XR not XR?? | ADHD Information

My 7.5 year old son is now taking 20mg of Focalin XR and we are finding that it works great but is out of his system in about 8 hours. Is this normal? I thought XR meant it would last up to 12 hours. The effects are great but it is out of his system by the end of school and he needs about 3 more hours to get through homework and after school activities. Anyone get a "kicker" after school? I am concerned that a "kicker" would take away his awesome dinner appetite.