My senior year math course (after Calc BC in grade 11) was discrete math at the community college across the street. Felt a little embarrassing for us to take up half the classroom, sitting next to adults, and realizing that most of us high schoolers were towards the top of the class. But other than that unfortunate situation, I think it was a good system, and if anything, cheaper for the school district than finding someone to teach in-house.
This is in fact how the programs are structured at many high schools with dual-enrollment. Most top high schools in the Bay Area offer such options for Multivariable Calculus and Linear Algebra. What Palo Alto is doing is dropping formal support of the program - in practice that has meant bringing college professors to school sites and providing these classes without fees for students. Without formal support, students have to pay and have to commute.