Not many. I went to a good school but still had to wait to first-year university to learn linear algebra. Assuming you mean "real" linear algebra with matrices, inverse matrices, determinants (please don't mention Axler's book), and linear operators.
I believe Linear algebra is/was taught in the pre-calc path of the provincial public curriculum (Canada) if you chose it as an optional thing. I did not.
It's common to find a little bit of linear algebra in a serious precalculus course, but nowhere near what's needed for ML. (For instance, I've never seen a precalculus course that covers eigenvectors, diagonalization, SVD, pseudoinverse, subspace projection, etc.)