US math courses for high schoolers often goes along the following path: Algebra, Geometry, Algebra II (basic linear algebra, but often not discussed as such, and other concepts), Trigonometry, Precalculus (1/2 semester each of the last two) and then Calculus. Of course, that adds up to 5 years so unless a student took Algebra I in middle school (year 8) they won't complete the full sequence, leaving calculus for college (depending on major).
The structure of formal proofs is taught in geometry. That's pretty much the only course where students are expected to prove theorems about the subject via proofs. In most of the other courses students are taught the formulas and techniques, axioms and theorems, but then apply them, rather than attempt to develop or prove them themselves. They're also, typically, not shown a proof of the theorems they learn, they're just told to accept them.