Student accounts are the only account type that cannot be deleted from within the account.
If you have a Student account, your teacher will need to delete the account for you, and this article shows step by step instructions to do so: Delete Student Account.
If you have a Solo account or an Educator account then you can delete your account yourself by following these few simple steps:
1. Click the settings icon.
2. Click My Account.
3. Click Delete Permanently.
4. Click Yes, Delete It Now.