How to prove that it’s not pseudoscience?

I’m 15, soon 16 and I suggested to my parents that I should go to a myofunctional therapist. We have been talking about ortho stuff for a while. The idea was shut down instantly, they just said it’s pseudoscience.

I have a recessed chin and a pretty long face with crooked teeth and a narrow palate, so I think it could be good. I have photos on profile btw

I struggle to mew correctly and If I get myofunctional therapy now it could really help me. How do i convince them???