My dad filed for me to get a Visa to the UK 21 years ago, I was 13 at the time but was denied. Now i want to apply for a UK student Visa, do i need to indicate i have applied previously so as to avoid opening old file or say no, i havent applied before for a Visa since its 2 decade ago? Its over 20 years now, do you think my record will still be in their system.

Yes. Disclose it as this will save you hundreds of questions at the POE. All your records are with them already so input your old passport number as well though it won't mean much as you were a junior at the time. Whats important now is if both you and your sponsor are capable of funding your journey. Good luck.

Pls share the visa link to us so we can check the criteria for you

Tabbyjones:
My dad filed for me to get a Visa to the UK 21 years ago, I was 13 at the time but was denied. Now i want to apply for a UK student Visa, do i need to indicate i have applied previously so as to avoid opening old file or say no, i havent applied before for a Visa since its 2 decade ago? Its over 20 years now, do you think my record will still be in their system.

If they ask whether you've been denied visa before, simply answer honestly. I see no reason to be dishonest.

@bolder, I don't think it's up to you to decide how long is long enough to justify not telling them. People get denied visa cause of these unnecessary lies.