J.H.
As mentioned GATE is the program offered by most schools. However, just because he's smart doesn't mean he will qualify for gate. GATE (Gifted and Talented Education) looks for other areas that indicate a child is gifted. The child must also display other aspects that indicate he/she is gifted or talented.
If he is bored, conference with the teacher to ask if he/she can assist in some independed challenging work at a higher level or if he can help struggling students or go into another class to help when he finishes his work.
Another option is to look for a Montessori School (Charter or Private). The Montessori method is designed to meet the child at his or her level and provide work to challenge him/her.