We sent our kids to the Independent Bonn International School for two years.
( About IBIS : [ on Independent Bonn International School ] )
We also sent them to the local "Grundschule" for a year. They were in 1st and 2nd grades when they went to the local school, and they were fluent in German in about two months. There are advantages to both the international and the local school.
57Hauler, PM me if you want to know more about IBIS. It is a great school, it costs Euro 10,050 per kid (USAF paid for our kids while we were there), and they have an outstanding staff and headmaster.