If you are receiving the same email notification more than once, it is usually because you appear on your school's Classlist site with more than one email address. This may be because you were originally invited by an admin user with one email address, but when you joined you registered using a different email address. You remain on the 'invited parent/non member contact' mailing list under the original email address and the Classlist system does not know that the person who owns that account has registered with a different email.
You can check by looking at the addressee in the email notifications you receive. If you are receiving the same message to different addresses, ask one of your site's Ambassadors (find them on the School page) to delete the original invitation which is sending notifications to the wrong email address. Alternatively you can choose 'opt out' on the bottom of one of the email notifications going to the wrong email. This will remove that email address from the mailing list system, leaving you registered correctly with a single email address.
Occasionally it happens that someone has actually registered twice at the same school using different email addresses. This is especially likely if there has been a delay between registering the first time and the second. Try logging in with both email accounts: if you find you have two accounts, just decide which one you want to retain and then go to the profile page of the one you want to get rid of. Under the personal details section, scroll down to find the delete account option and click 'Remove'.