There's no rule in life that says the only place you can learn things is in school.
Self-teaching the maths and physics may be tough, but it'll also put you in a good position with your study skills when you move onto the more aviation specific stuff. Use it as part of your personal build up.
Then do the PPL first! Don't get sucked into spending huge amounts of money *until* you've done that component to tell you if you have the real passion and attribute to learn to fly. Then, if you do, move forwards to the professional training.
G