I agree with TonyWK, school is not for everyone and some people even need that year or so o'off' getting real world experience before coming back and completing they education as Mature Entry students.
This has not been an ordinary year and for many of us that has added stressors, if your son is disagreeing with you on a point, like what movie to watch as a simple example, asking them what alternative they might prefer to engage them on the process more can be helpful, alternatively if you try boiling the decision down to two options (both of which you are happy with) for them to decide between, does that provide enough of an illusion of control for the child?
Teen years tend to be when people become egocentric and their issues and worries trump all of those around them. Part of growing up is them, realising that it's not about them, and when it is about them, you act in their best interests as their parent.
Also parenting support websites can be a good resource: https://www.dss.gov.au/families-and-children
If you are intending on continuing with your current partner, who makes you happy, great! Having a conversation with your partner about the situation to get their feelings and observations may help you parent your child, they may also be willing to co-parent, that is something to discuss so you both have clear idea about expectations.
Talking with the child about your dating situation may also help if the child is "acting up" out of any perceived loss of attention, because for children attention=love. Finding alternate ground for you to spend time together may help maintain the 'family' he perceives as the two of you.
Just ideas to ponder, hopefully helpful.
