Have you experienced tutoring someone like my yr 11 son , who does the bare minimum in school , isn't predicted great grades but has the potential if it wasn't for his oh so annoying teenage miasma of laziness and disdain for learning?
Oh yes. I know it's incredibly stressful and frustrating trying to educate someone who doesn't want to learn. It must be a difficult situation and you have my sympathy!
If you'll accept some unsolicited advice...IMO the best thing to do is to have a light-hearted, non-critical chat that begins with "Any idea what job you might like when you're older?" Try to bring this up in a casual conversational manner so it doesn't seem like you're trying to have a Serious Talk with him. Once he's listed some jobs, say (again, cheerfully and casually), for example, "Okay, so if you want to be a TV presenter you need to have great communication skills. It's probably important to have good marks in English. You also need to know what's going on in the world so probably a good idea to learn about history and politics." Or "If you want to be a football coach you'd get better jobs if you also know about physiotherapy. Studying biology and chemistry would be a good start."
Try to avoid giving the impression that you're telling him what to do. But I realise that's much easier said than done...best of luck, hope the situation improves! Might be worth taking him to a careers advisor who is separate from his school if that's a possibility?