We are glad you are reaching out today. We can appreciate your concern and frustration. Did this behavior come on rather suddenly, or was it developing over a period of time? Have these always been issues? Has there been any other changes in his life, such as changes of friends or social activities? Has there, or was there, a traumatic event prior to any changes taking place such as a death, or break up with a girlfriend? Are you aware of any drug or alcohol usage? These are issues that can precipitate these type of changes, if in fact these issues are changes.
Failing classes for not turning in assignments is concerning. It would seem this would be a priority. Let him know it is unacceptable, and have him create a plan that will address it. Perhaps staying at school and turning in homework prior to leaving, if that would be an option with the school. If it is too late to save the classes, perhaps a summer school program is in order.
You mentioned you are constantly telling him to do his work, what you expect, and handing out consequences, yet that is not seeming to work. As parents, that can feel like we are trying to force a square peg into a round hole. While the consequences seem appropriate, we can also try to connect with him to see what is important to him. When we can connect to him through a "what's in it for me," he may be able to make connections between the behavior and it providing something he wants.
Family counseling could also be helpful to get issues out and develop strategies that all can commit working towards. It may be that since it is "NOT ok to fail," he is feeling and reacting in a way that it is not worth trying. Sometimes the fear of failure will drive one to avoid the possibility of it.
Please remember we have counselors available 24/7 at 1-800-448-3000 to offer support and assistance. There is no question you love your son and want the best for him. Challenges such as this can be stressful for all. Stay strong, keep reaching out, and keep trying.