[graemep]

Depends on how much income they get.

Under 16s also pay income taxes in they have income. They also pay various other taxes such as VAT. Non-citizens pay taxes but do not get to vote.

The general expectation is that they should be in full time education or training until they are 18.

All that makes "a minority of people in this age group pay taxes" a very weak argument for giving all of them the vote.