or does one need the international student ID?
In general, you can use your American uni ID.
Can’t hurt to try, London Walks was always good about accepting American student IDs for a discount.
@Tom_MN
I've used my American uni card when I was back visiting in Spain and other EU countries and it worked every time for student discounts.
How is one to tell a difference between an American and EU uni ID?
In my experience (as a graduate student for many years, so many trips and places where I tried to use my ID), it comes down to whether the site considers the discount to be for students generally or something offered (possibly because of funding) to students in the local area or region. If it is for students generally, than any student ID that seems valid is accepted. If it is a special rate for some specific group of students, than an American ID won't work. I only remember a couple of times when my ID wasn't accepted and a couple more times when they couldn't decide if they should accept it or not but did.
Reduced admission in the EU is often limited to students of EU/EEA/Swiss universities so unless the museum or other place decides to extend this privilage to all students, your US ID won't work at all. This sometimes provokes comments about discrimination but under the EU law, institutions and services financed by local/EU taxes, funds, grants etc, are allowed to discriminate against non residents.
Funny story--on a trip to Rome years ago we visited the Roman Houses under San Gregorio. I noticed there was a discount for senior citizens. My husband had turned 65 so I asked for "il scent per uomo vecchio." He got the discount; I suppose because he looked his age. Students would have to document their status. . .
related to SusanD - we just returned from Italy Switzerland and France ... my husband tried to get the senior discount and was told he had to be e EU citizen. We talked to some students from UCF we met in Florence and they said they had to use their ID from the school in Italy they were taking summer school classes not their UCF ID to get student discounts.
I traveled across Europe with my kids (Netherlands, Germany. Austria and Italy). I had no problem getting reductions for my children until I got to Italy. I was regularly refused in Italy because we weren't EU. Always ask but expect you may not always get a reduction.
Tower of London - my 2 over 65 years of age cotravelers got the senior discount tickets there, we're all from the US... so yeah, it varies all over the board.
Don’t bother with international ID but do have your students bring their ID. My students got discounts in Italy and Greece but sometimes it was age related rather than student based. In other words, a passport would have worked as well. EU students often have free admission but not so for nonEU students.