This sounds like a really cool project. I know from an American
perspective, it is very easy to develop misconceptions and stereotypes about other nations, without every having met someone from any of those nations. I had an orientation about a month ago for the program (AFS) that is sending me on my student exchange to Germany. All of the foreign students who were in the US for the year were there for their midyear orientation, and it was really amazing as an American to meet more foreign people in one place then I had ever met in my life. I got to talk to people from around the world, and my biggest impression was how similar people from all over the world really are. So I think something like that, that gives
perspective is really a great thing. You'll have a few problems though.
Number one, language. Are the majority of your Dutch students Dutch/English bilingual, much like many Germans are German/English bilingual, or do they only speak Dutch?
Your second is going to be contacting other schools. The more countries you try to integrate, the more difficult it will become. You might want to contact a student exchange program that has contact with foreign students between the ages of 14-16 that have lived in the Netherlands, and see if they would be willing to share their experiences with your students.