My exceptionally headstrong kid has come to understand that I am on his side, and that is exactly why he is required to work whether he feels like it or not. It took about half of one academic year of dropping out of all social and leisure activities that took place during normal school hours. I also removed access to all remotes and toys during school hours. I locked the computer with a password so he could only get to school applications. We became the kind of homeschoolers that stay home and do school. I firmly established a routine - got him up early (and I do mean early...6:30 or 7, and had him working while he was still sleepy.) immediately ate, dressed, brushed teeth, and got to work. There was simply no way out for him. No leisure or play except very short breaks until all the work was done. If he made it take all day, that was his problem. He was only wasting his own free time. He could not outlast me. I would stand over him and enforce what was required until bedtime if necessary. This totally reset his expectations. He's now very good about doing his work and gets it done in half the day. I'm so glad I didn't waste time trying to figure out how to make him happy about it, or begging and arguing. He's learned that he has to do it - a very important lesson. Now he is happy because he has good work habits, gets his work done and then has a lot of free time. We are also very busy in the afternoons with those "other" activities, so this is a good balance between academics and leisure/social activities.
It takes a very strong commitment to see this through initially, but it does not go on forever. If you never give in, eventually they get it. And then the days are easier and more productive, school can actually happen, progress can be made, and the household can be peaceful without a lot of stress about behavior and school.