Personally, I do not take on students that have no self-interest in learning the instrument. This is made very clear when students/parents audition for my studio. If parents are very insisting yet the student seems to show little interest, I will refer the family to other teachers. Does your student communicate or at least hint at what the tantrums are really about? He may be trying to send a message, yet parents haven't picked up on it.
I would take this child away from the piano and offer him a smoothie instead, and then have a relaxed conversation with him about anything ... probably something will pop up during this talk, I agree that he seems to communicate something, there is something on his mind. It may be something that has nothing to do with piano playing as such. So you have to be a mentor instead of a piano teacher for a while. Or, if the chemistry between you just does not work and you don't gain his trust, tell his parents so and refer to another teacher. Also point out to the parents that forcing him to do something he does not want to do, will only do you all harm.
All of what was said is great advice. What I would do is have the parents attend the lesson. If he continues his destructive behavior they can see it and come to their senses or maybe they know methods of calming him down to focus on what he needs to. Maybe he is a perfect angel when their around. If his behavior improves you could just have them stay in their for every lesson.
...Try and find the trigger. If he sometimes complies to your directions and suddenly does not there is usually something that cause his behavior to switch to a distracting one. It may be when you require him to play by himself that he suddenly acts up. You can better prepare him for it by setting up a type of game where I play something then you play something and build up independence for example. I am not saying that is the problem but you could try and find the root of the cause. ...be real with the student like another person wrote. Have a good heart to heart and say "ok , I know you do not want to play piano but you are already hear so why don't we make it fun for you.