my parents were saying to use the school’s application for schools that i am REALLY interested in because it shows that i take time to fill out their application over using the common app to save time.
i understand what they’re saying, but is this actually the case?
It isn’t the case, but your parents have a good point. Many colleges have parts of their own app that can be filled in and submitted separately. My daughter did this for several colleges, and she got in or was waitlisted to those colleges. She submitted the informational parts of the college app and submitted the common app to those schools for the remainder. I think it’s a good thing to do, because it shows you took the time to look at their website. And speaking of that, do look carefully at the college website. We found more than one college had optional essays that could be submitted that were NOT part of the common app. She got into those schools too.
Are there many schools that even have their own app if they take the common app? I think for my D there might have been two.
No, because colleges have supplements uniaue to then, that’s where you show your knowledge of the college and how it fits you. You also demonstrate interest by filling out the request info form and communicating with admissions.
Often colleges appreciate the common app because it’s standardized so it steanlines their process.
Which colleges have both a specific app and a common app?
Typically you’d use the common app and take good care with the supplements.
No. I’ll let you in on a secret - parents are sometimes wrong. 
There is no college in the country that asks applicants to read tea leaves. If the college wants something specific, they will tell you. If they did not want students to use the Common App, they would not partner with the Common App. As others have said, they may have supplemental materials that they require/suggest… As always, read the admissions website for the college to ensure that you are submitting everything they ask.
Almost every school my kids applied to required its own supplement, in addition to the Common App. I think my daughter applied to just one school that only required the Common App. Applying to college is a lot of work!
Oh, and if the college “suggests” something, and it’s a fairly competitive school, you should take that suggestion as a requirement.
My daughter’s school takes the common app but also has its own. Its application is free and short. The common app is longer and costs money to file it.
It’s the applicant’s choice, but I really doubt the school gets many on the common app.
I’ve heard admission officers at many colleges say they don’t care which application you use. The two times my S used the school application was only because he got a waiver for the application fee which he found easier to use with the school application.
My D used the common app every time she could, even if the school had their own app. Why type information more times than you need to? We asked at info sessions if it mattered and they always said no. I realize this is just one data point but she was even accepted by her reach school using the common app instead of their app.