Yes I should hear opinions of parents who currently have their kids in those schools, but it is very hard. I've made same threads in four different forums, one of which was Japanese expats forums, yet I've only received a response on this one. My husband has colleagues with children who live in Paris, but their kids are all either much younger than 16 or staying in Japan.
I do expect to hear various opinions. In fact, my daughter loves her current international school and their teaching style fits her well, even better than her previous high school in Japan which is said to be one of the best. However, at the same time, half of her classmates and ex-classmates say that the school is horrible (she does agree though, the equipment is poor as the school is really small (7 students in her class).). I personally don't think the school is the best place to continue her education, especially equipment wise (it seems to be really poor for her interest, science), but equally I am happy with the school as long as my daughter enjoys the school and succeeds to achieve good grades in her IGCSEs.
Well, at the end, even if a school has good reputation, it will all come down to compatibility I guess.
My daughter's already checked the websites in every corner. She said the university list was only available on the ISP website, which had a few good universities on it. Other websites were not as informative, sadly.
The most frustrating thing is that we were informed our transfer just before the Ski Holidays, and unluckily, our region's holidays are at the same time as Paris. If our region's holidays were a bit earlier or later than Paris we would've gone to the schools and checked them out ourselves but now those schools are closed and after the holidays my daughter will be busy revising for May/June IGCSEs and my husband will be busy with work. 
Well, about French universities, I don't think my daughter is interested in studying in French. If she did, she would've entered French a high school already. She is just interested in being able to speak or write French at a decent level, as it's her third language after all. She often wishes that she could come to France a bit earlier though, looking at little kids in her school. They become fluent French speakers just by being friends with French kids (grammar is horrible but it can be fixed quite easily as they get proper education).