Account for teen (UK)

Read here: What Is the Minimum Age Requirement to Use Garmin Connect?

From the legal point of view Garmin has no right to collect data of minors. You could circumvent it by creating an account with your credentials, but of course, that is not legal.

There is also an app for kids (personally I know nothing about it): 

Using the Garmin Jr. App Kid Mode 

Thanks. The Garmin Jr account (and devices) seems to be for little kids. It seems odd that a parent could set up and manage an account for a small child, but not for a teen.

Are teen athletes just banned from using fitness apps?

1908978 said:

Are teen athletes just banned from using fitness apps?

I am afraid that in many countries today the legislative is indeed made in such way, that it is extremely risky to try to collect any personal data, and at underage persons it is even much worse. The companies cannot afford doing it without risking huge fines. It is up to you whether you want to violate any local laws, and take the responsibility to create an account for them in your name, or under a faked identity with a legal age, but the company cannot really do it without risking legal actions against themselves.