International Student Discount Card...

In France, student discounts are only available to EU students. I don't know if an ISDC would work. A regular student ID for a university in Europe would.

For a two week trip, I doubt an ISDC will pay for itself.

I found that ISIC cards are best when traveling to the US. When I was 18 I toured North & South America for about a year, and ISIC gets me discounts on Amtrak which I used to get from one city to the next. I hated bus rides. I still have an ISIC card when I was 21 and traveled all over Europe. I never used it because I have a school ID from when I did a semester in Sorengo (CH). And I bought a Eurail Global Pass so there wasn't a need for student IDs. But you have to be an EU citizen, 18- 25 years old, to get free admission at the Musee du Louvre, Musee d'Orsay & other monuments on their free nights (usually the first Sunday of every month). Either way, I'd avoid those free nights if I were you. It gets really crowded. Unfortunately, I can't remember if there are student discounts in Paris attractions. Children get in free at some museums though. Some West End shows have student tickets as well. I think in UK, school IDs would suffice. If you will be stopping by Paris and London, I would recommend getting a London Pass, a Paris Pass and Paris Museum Pass to save on admission fees. They usually sell them bundled with a travel card/metro pass.

I remember there being only a coup,e of places that I can remember in Paris to offer student discounts-one was Musee d'Orsay. I used my student card and got the deal. That should be sufficient for your travel companions.

In my experiences, I always just brought my college ID card when I traveled, and when a place advertised a student discount, I would present it and ask if I qualified. I don't recall ever being told no. Of course that was about 8 years ago now, so things may have changed.