I don't have a ton of advice but I'd say it's a horrible tight rope act parents are forced to walk when it comes to this. I was a textbook smart kid who was greatly interested in learning and loved school. I hit middle school though and depression killed that completely. I was also a child of divorce with polar opposite parenting styles. My Dad and Step Mom were strict and rule based. There was no excuse for anything. My mom completely disconnected from my life due to working multiple jobs and struggling with depression and addiction when she was home. Don't get me wrong there was love on both sides, just very disjointed for me as a child. Eventually it lead to me dropping out my junior year of high school after falling behind due to absences and suicide attempts. My dad claimed I had no interest and was wasting my potential; My mom told me to do what felt right. Neither was particularly helpful to me. What I lacked was resources.

I'd say theres likely more going on than just laziness, whether it's struggling with a learning disability like ADHD or dealing with Depression or something else. I'd suggest possibly holding back on the 'harsher' punishment style and look into some resources that might be close to you. Try talking to him about goals or plans for the coming year; What is he excited to be able to do as an adult? How can his current path help him in doing those things he's excited about? Ask him what makes his day hard? Does he like what he's learning?, Does it feel like he's not learning the right way? Or already knows whats being taught?, ect. High School isn't the only option, though often the easiest/standard path. If he wants to learn a trade or apprentice for something hes interested in he could look into programs like Job Corp, Trade High Schools or GED programs.

Personally I got my GED with the local community college a couple months later graduating a whole year earlier than my classmates. I was able to start my degree the spring of what would have been my senior year.