Hey Aayush.

Greetings. Hope you're doing well. School leaving certificate is provided to allow you to seek admission in same university whereas transfer certificate makes you eligible to seek a seat in a different university. However they are no different, since they are issued by a school to prove that you've completed your 10th or 12th board. Even if you're leaving a school, say after 4th grade, you'll require transfer certificate which is as same as leaving a school.