My kid refuses to do his homework and is failing freshman biology, literature, US History and Art in high school. I grounded him and he still won't do the work. I've taken away as many privileges as I can. What now?
If your son is already failing all those courses and not doing homework, then it is probably too late for grounding to be effective. Sometimes I question the effectivity of grounding at all in teenagers, but that is beside the point here. Your son is becoming independent, and he has reasons (however ill-founded) for deciding to not do the work. Negative motivation is not going to overcome his reasons. Without more details it is difficult to determine what might be going on, but this is definitely something that you should sit down and have an open discussion about with him. You should let him know that he is free to express his thoughts and opinions on the matter, and that you are primarily interested in knowing why he feels his school work has fallen by the wayside. Now that your son is getting older it is time to start treating him like an adult. He may not always be prepared to make the right decisions, but he needs to learn how to make decisions on his own and face the consequences when they arise. You can still provide him guidance at this stage, but you should always keep your communication with him open and calm. Speak to him like an adult.
You are (were) a teacher, does it work if you sit down with him and assist him with his homework? It may not be a long term solution, but might be enough to get him kick-started.
The broad spread of problem subjects probably shows that it is not one subject that is difficult, rather a greater motivation issue.
We found with our daughter (12) that there comes a point where neither punishment nor bribery works. The best thing we've come up with is working with her on her sports/school. the downside is that they don't develop the self motivation skills required later on in life. It's a balancing act.