Recommended ghost tours in Paris?

Less macabre but plenty spooky enough would be a wander around Père Lachaise cemetery. I don't personally think an organized "ghost" tour is a necessity - although a google turns up any number of those - nor can I recommend one from firsthand experience, although I've had my own looooong wander there. What you could do, however, is download a map, and have your son research online some of the rumored hauntings. Just a few of those:

https://thelittlehouseofhorrors.com/pere-lachaise-cemetery/
https://www.huffpost.com/entry/9-most-haunting-graves-in_b_8357276

Map:
https://www.api-site.paris.fr/paris/public/2018%2F9%2FCPLMapEN.pdf

Hours and stuff:
https://en.parisinfo.com/paris-museum-monument/71470/Cimetière-du-Père-Lachaise

Thank you, we did go to Pere LaChaise and he absolutely loved it. HIs favorite visit of the trip so far.

You did that today? If so, I'm so glad that it was a good replacement! I loved it too but for the camera and some history versus ghost stories. :O)

Paris Charms and Secrets does a night time electric bike tour. No idea if it's spooky, though. We really enjoyed the day tour with our 12 and 14 year olds. You ride somewhere, hear a story while looking around, and repeat.

You could see if you can get into Le Musee des Moulages in the 10th Arrondissement. It's an antique medical museum with thousands of wax anatomical models made in the 1800s showing body parts afflicted with various diseases that people actually had. It's pretty creepy & a little gross. Just the sort of thing a teenager would love. They aren't always open though, so you'll want to check in advance.

If it's closed, tell him to check Atlas Obscura. There's hundreds of odd and off the beaten path listings there, some of them kind of dark & spooky. Lots of small churches with bodies & bones of saints in glass coffins on display, animal taxidermy, etc.

Atlas Obscura! Great idea. I know it but forgot to look at it. Some good ideas there that he will like.

AirBnB has experiences as well as places to stay; I took a ghost tour last October - it wasn't OVERLY spooky but late October, 630 p, and VERY historical (the guide was American and had a French History degree, so he knew his stuff), I would definitely recommend. Started at Shakespeare & Co and ended where Henry IV was assassinated.