Hey internet stranger. Here is another internet strangers 2 cents on Catholic High Schools based on my personal experience.
TL:DR Education is good, but the school might make it so they can't take the classes they want or need for Religion Class (unless they mess up). And at my school there were cliques that socially isolated me and many others, with unchecked bullying which felt encouraged by the staff. I am happy I completed it, but I'd wouldn't want my kids to go through the same thing.
This happened over a decade ago, but the school I went to was both good, and very, very bad. The pro was why you are considering it. The education quality is much higher than the local public school. I was prepared for University much better than those I meet at the University I went to, who went to public High School.
The con was two fold. First some education options were denied to other students due to "optional" religion studies class. Technically a school can't force a high schooler to take religion where I went. But the check box for that course was always checked before I got the class sheet. Which meant that I couldn't choose what optional courses I wanted if it overlap with that religion course.
On a side note they messed up 3 ways in my last year. They couldn't get me in a gym class for gr 12, so I had to goto a gr 10 class, then I took a CAD course which I wanted and a coding, but by the time they realized I wasnt taking religion, it was too late. I was given a speal on how I couldn't get a religion high school diploma, but just the normal one. It was fun especially since.
The second big con. The school was extremely cliquey. Like debilitating so. I was from another community, my bus ride was an hour away. So in Gr 9 I tried to make friends... But the cliques were already made. And I as well as many others were socially isolated. I didn't find the misfits hiding away at lunch in the media classroom until like gr. 10/11. There was another crowd in the art room. This attitude sadly felt encouraged by some the staff, and bullying was out of control, it often resorted to physical violence more than once. I stayed off of the radar but I hated those 4 years. If it wasn't for my activities outside of school I would've been in a really bad state.
With that said, there was another (3 in total) Catholic high school in my local area, which my extended family went to. Apparently the one they went to was so much better.
Retrospectively, I understood how much of a benefit it was to go there. I am happy I was able to stick it out. But I would do a lot of research before putting my kids into a Catholic high school since I don't want them to have a repeat of my time.