Need to see in...

Valerie - assume you have read Diary of Anne Frank? It was the most memorable experience for both me and for my daughter when she when with her friends. Very understated - not a big "interactive" museum or anything like that. Just the feeling of Anne being there from having read the book.

And be sure to eat french fries with mayonnaise and the mussels in Brussels! I'd also recommend the beer, but if it is a school trip they probably won't let you drink so don't do it if it is forbidden - had friends with an 18 year old who drank a pint in London (legal there) but was sent home because it was not allowed by the school.

In Paris there are about a million amazing things to see, but one museum that I absolutely LOVED was the Orangerie. It is a small art museum that houses eight of Monet's Waterlilies paintings, and then it has an Impressionist gallery on the bottom level. The Monet works are huge, they take up an entire wall each, and they are gorgeous. If you are an art-lover, then make sure you see this museum - I found it much less crowded than the Louvre and Orsay.

You might want to wait until you see the actual itinerary for your trip before planning your free time. Undoubtedly, many of the "must sees" for each city will already be planned for during the group time. I wouldn't plan on having any actual activities planned for the free time, anyway -- use that time to just hang out and experience the city and browse in the shops.

I have to agree with Nancy- use your free time to "people watch" and shop. Most major and many minor sites are included in your typical student tour. Find a local market or public square area and hang out!

Let me give my nomination for chocolatier not to miss in Brussels- Moeder Babelutte. If you visit Brussels as part of tour, you'll definately pass this shop, on the way between the Grote Markt (Grand Place) and the Mannekin Pis. One taste of their pralines and you'll experience complete chocolate nirvana.