To settle an argument in our (wider) household

How old are "traditional" trade apprentices when you take them on?

Member of family (she who is *never* wrong, supported by clutch of
offspring) was adamant that no-one can leave school before 18 YO.

So I said "they can if they take an apprenticeship", to which the response
was "only one of those waste of time classroom type apprenticeships" (no
argument from me about the "waste of time" part here!)

and I said "No a traditional trade apprenticeship counts" - "Oh no it
doesn't" .....

so what is the rule here please?

TIA

tim