My DCs went to a 3500+ student suburban public high school (age 14-18) in the US.
The US liberal arts approach to education was adopted and adapted from the Scottish system, which emphasised breadth and sought to develop academic all-rounders.
My DCs were all placed on an honours track initially, where their classes were taught at an accelerated pace and thinking and writing skills of a higher order were expected. These were rigorous classes, and they were expected to be disciplined self-starters, interested and engaged in the subjects, and willing and able to work independently.
Other tracks suited different general abilities and learning styles.
In a school so big, dozens of courses were offered across all academic departments, and kids of all ability levels, potential, and with all sorts of post secondary aspirations could be catered for, from astronaut to auto mechanic.
The honours track was for kids who were pegged at age 14 to be capable of admission to very selective universities. Because these universities like to see evidence of either ability or the capacity to word hard, students aiming for those universities took a broad range of subjects, with English and math taken all four years. Other requirements for these universities were (usually) at least three years of humanities, three or four years of lab science, and three or four years of a mfl. Students did daily PE every year for four years too. PE included drivers ed and mandatory health coursework. This left little room in the schedule for the school and state graduation requirements - at least one year of fine arts, applied arts, consumer education, civics, keyboarding/ business administration, and more, but summer school and online courses were available to complete the tickbox courses.
The 'market' pretty much dictated the courses and the level at which courses were taken in high school. They moved on to universities where their liberal arts education continued with core courses, aka general education courses for two years, followed by two years of their chosen major(s). They all did Calc III by the time they graduated from university, as part of their core coursework, as well as advanced mfl (between them all, the mfls were French, German, Latin, and Persian), philosophy, psychology, history, lab sciences, and economics.
I really like the liberal arts model. It delivers exactly what it promises - a well rounded and versatile graduate who has shown ability to put his or her ears back and work hard at subjects that don't necessarily come easily.
Marking of coursework at high school level was done by teachers, with the double check of nationally administered standardized tests operating as a method of quality control.