How to Tax exempt child sizes?

In the UK, VAT (Tax) is 0% on children's clothes.

If I have a product setup with several sizes. How do I apply a different Tax rate to specific sizes (attributes)?

Or how is this requirement normally handled?

AppSoft wrote:

Tax applied on whole order or product by tax category. not on attributes. seems you have to customize that part by yourself.

Thanks,
Jatin

Customize, or consider creating two products - "... - Child" and  "... - Adult".  Then use Tax Category on product.

Looks like duplicate products are the best way to work this and how we have done it in the past. However the product range has come from a client import making it an extensive task.

Very surprised this isn't an option as it would seem a common requirement.