Trip with teens

London, Amsterdam or Lyon. Those are all quick train trips from Paris.

London is very expensive. So they like to hike, so how about Amboise and bikes? not far from Pairs so you will not waste a bunch of time or money on travel. I took my grandson there when he was 15, we had a wonderful time, and bike rentals were cheap. J

By limiting transportation to a train you are severely limiting your options.

Amsterdam. Im biased but someone already said it so I'll piggy back. My kids have been several times and it was great with kids. First, there is a lot of English spoken so it makes it feel more comfortable. Second, the bikes and the canals are unique and fun (we rent bikes when there, although it's not for the faint of heart so your mileage may vary). The NEMO children's museum is interesting, even if they are teens, and it has a roof top deck that has fountains on it (like, water squirting into the air that you can get wet in) and a cafe with food and drinks (non and alcoholic) and a view of the whole harbor area around Centraal station. Of course, if they have read Anne Frank in school, you could go to the Anne Frank Huis, or the Jewish history museum. And they have probably heard of Rembrandt and Van Gogh, and seeing those at the Rijks and Van Gogh museums are powerful. As for food, Amsterdam isnt cheap either, but there are many casual places to eat, and you can always get picnic food at a grocery store and have lunch long a canal or in Vondelpark (also we tend to stay in apartment rentals so we have a kitchen and save that way but Amsterdam and Paris have drastically cut down on those so this may not be a more frugal option anymore).

By overnight train you can consider Berlin. Enough highlights, events and a huge city area to power them out as well as enough food for fair prices to feed the "Scheunendrescher" (combine harvesting machines), German saying for people who eat a lot.

Get the teens involved with the planning. They probably have different interest, so perhaps include things for each one. To paraphrase an old saying, if the teens are unhappy, everybody is unhappy.

Last year we did Paris and then took a train to Stuttgart, where we rented a car and did southern Germany for a few days (Rothenberg, Fussen). My teens loved it. Very easy to drive in that area and the train ride is 4 hours, getting you away from the Paris traffic.

With 8 days, go somewhere not too long a trip from Paris. Does your 8 days include arrival day? If so, figure on 3 days one place, 4 days another. Figure a half day for changing locations. Get open jaw flights so you don't have to backtrack to return home. Amsterdam is a good choice for older teens, as Jessica suggests, and an easy train ride there. It isn't cheap, but cheaper than Switzerland.

As a mom to a teenager, I second the suggestions to visit Amsterdam with Paris and renting an apartment with a kitchen to save on food costs. (So much food!!) It will also be easier and probably less expensive to find an apartment than a hotel for 4+ teens/adults. We have booked apartments through booking.com and air b&b in Paris, other cities in France and in Italy with no issues at all - despite the well intentioned “warnings” from some folks on this forum. I know you’ll have a wonderful spring break trip!

London is expensive. So is Switzerland.

You could consider places like:

--Freiburg / Black Forest (nearby options include Colmar and cute villages like Eguisheim or Riquewehr as well as places like Gengenbach, Calw, or St. Blasien)

--Grenoble / Albertville / Aix-les-Bains (be aware depending on when in spring that weather may be a factor up in the mountains)

--Verdun / Nancy / Metz (maybe with a side visit to Luxembourg or even Trier)

Those are all reasonable from Paris, great for nature lovers while still being classically European, and have enough tourist infrastructure to be easy while still being less expensive than a place like London. All would be great places to rent a place with a kitchen so you can avoid eating out every meal. The Freiburg / Black Forest choice may be your best option for public transport.

You could save some of your very limited tourism time with a multi-destination flight itinerary. Fly into Paris, fly home from Amsterdam, on one complete ticket, often for not much more than an ordinary found trip. Myself, I could spend a week in Paris and still ache for more (I've been there more than a dozen times.)
Now, some advice you did not ask for. These young adults should help with the planning and research so they will feel it's their trip too. Insist they develop a food budget to inject some realism into their excursion.

With teens, Amsterdam staying in Haarlem.