International schools in Athens

I am French married to a Dutch partner and we considering an assignment in Athens. I am looking for information and tips about international schools in Athens: I have made a pre-selection St Lawrence, Campion and ISA based on the websites but am eager to hear from parents with children in those schools. My boys are 12 and 9. They both will have to improve their level of English before they can fully adapt to the cursus. Thanks in advance.