Question regarding Junior Ratings

How does one get classified as “junior” for ratings?

My primary (middle) school has now been added to the CodeChef database, and I added my DOB to my profile yesterday as I had a rating but didn’t appear in the ‘junior rating’ list. Will I be added to the junior ratings automatically now that my DOB is in the database?

DOB is not important for junior ratings. You are identified Junior from your institution. Suppose you add institution as a school in your profile today, then your junior rating will be calculated from the next contest onwards.