Hello, I hope you are doing well

Even if you are a private candidate School Leaving Certificate is necessary for admission in most of the colleges. Some colleges may not ask for it but if you are asked to or if it is mentioned in their brochure you will have to submit SLC. The school from which you did your class 12th will give you your SLC, it's not that much of a problem.

Even if somehow you get admission without SLC, it is necessary to have SLC with you, it may come in handy some day.

Hope this helps