What does this mean?

When my mother tried creating an account in Gateway To Prep Schools, but this happened:

Unfortunately, registration must be completed by your parent/guardian in order to comply with federal privacy laws. Please ask your parent or legal guardian to complete the registration. For technical support, parents/guardians may submit a technical support request. Applications received from an ineligible registrant may be rejected.

How would we fix this?

Did she put in the correct birthdate?

It means she should ask Gateway:
https://applywithus.kayako.com/gateway/Tickets/Submit/RenderForm/3

^ Yes definitely- and maybe give the school(s) a heads up that you’ve encountered a problem with Gateway and you’re in the process of working it out.

Like everybody mentioned above, either it’s DOB or a problem with the email address. Try to use an alternate email account.

Thanks for all the help!

When I was 10 I was looking at GTA V trailers online and I put my real DOB on the XBOX website and it blocked me from viewing the site. Just delete your cookies in the history section if your on Google Chrome or any other browser. No need to create a new email. Good luck on your application!