The AIS as in Australian International or American International?
Our son will be in a PIS within the ESF umbrella and we chose it over the Aussie International because of his age. He would have been one of the youngest versus one of the oldest. Norwegian seems nice. We thought about it but there is no follow on high school so since we were planning long term and knew how competitive each passing year gets, we decided for a through train school i.e. Grades 1 - 12/13.
If your son was born in 2005, in ESF, he'd be in P2 (it really depends on the month of the birth). The Aussie International which also follows year and month, has a different system. In the local HK system, he'd be in P1 this September.