Have you done any research to see if there are any apprenticeships or courses related to practical jobs in your area?
Perhaps if you spoke to your parents with some feasible alternatives to A-Levels in mind, it would show them that you're serious about doing something more practical, and that there is a clear route you can go down. They could just be worried that if you don't do A-Levels, you won't have as many options in the future- but apprenticeships/BTECs etc are a good alternative to A-Levels and would probably suit you better if you're a more practical person.