How do I convince my parents to fund stuff

[Deleted member 19766]

I'm not talking about cosmetic surgery but more health surgery and doctors appointments and stuff, I need to get my palate expanded, I might need septoplasty, I will probably get my permanent retainers removed (6-tooth) and replaced with 4-tooth ones, a personal trainer (Or some other posture expert, not sure yet) for my fucked up asymmetric imbalanced posture that was caused by ties in mouth (All totally removed, I just need to keep strengthening) and maybe myofunctional therapy for my bad facial habits/lack of lip seal. This is all purely medical and would help me greatly both mentally and physically (Fix sleep apnea and TMJ) but my parents are stingy fucks, I am a senior in highschool with shit grades btw and the clock is ticking (I kinda need to do all this stuff ASAP). Any advice

Edit: I forgot to mention this but I might literally need bimax as well JFL