If you are under 18, your Tier 4 visa application will need to include extra documents, including your birth certificate/household register and a consent letter from your parents/legal guardian.
The letter will need to confirm the relationship between you and your parents/legal guardian; that they give consent to your visa application, and give consent to you travelling to and living independently in the UK. The letter must be signed by each parent unless only one has sole responsibility.
Make sure that you read the Tier 4 information on the International Student Support website.
For more information, please log an enquiry online with the Student Information Desk (via the SID tile on iExeter).