If your son isn’t interested in anything to do with school, then you need a properly under-hand and secret squirrel (ish) plan to get him engaged in learning again.
First, stop nagging. Nothing will be achieved this way. Second, get outside – visit some places that sound like his sort of thing and don’t mention at all the educational angle. Get on to a ship, take him to a play, visit a farm, or an exhibition. Play the whole thing down like it’s just something to do on a miserable afternoon.
Start talking about stuff in a natural way – interesting questions that come out of what you’re doing and seeing. Take it slowly though because if you come over all eager and over-enthusiastic he will smell a rat. Perhaps make comments about opinions in the sports section at the back of the newspaper or ask him about something you hear together on the news in the car.
Next, up-style his bedroom. It’s likely to be a bit tired and forgotten since you decorated it when he was younger (or never). Recycle and remove all the things he’s grown out of and liven up the walls with a poster of something he’s interested in. Go with planets, mechanics, breeds of snake, anything that encourages further investigation. Set up a desk and a chair the right height and get a cheap lamp from BHS or IKEA. If you can stretch to getting him a basic e-reader then do it – it’s a great way of inspiring him to read.
And when you talk to him about school, get really involved in a conversation about the most interesting parts of the day, even if it’s his game of football at lunchtime. Once the dialogue begins it will naturally shift towards the areas you prefer in the future. But keep a light touch at all times and his level of engagement will improve.