Streaming isn't the solution.
Tracking is better. Many American high schools offer courses at various levels, and the idea of progressing through school with same age peers toward a final exam would be considered strange. Tracking is based on aptitude testing done before students start high school. The track you're on isn't set in stone - if you want to change and show ability, you'll be able to chop and change. Tracking is also related to style or preference in learning - self starters vs kids who need a lot of teacher input.
Especially in maths, kids do classes with students working at their level. A 14 hear old who has advanced to calculus could sit in class with students of any age from 14 to 18.
Large schools with huge numbers of staff on the payroll make it possible to offer subjects at a lot of levels, from remedial to university level, and even niche topics, for instance, in English lit courses that appeal to and engage different groups - War and Literature, or The Victorian Novel, or Literature and the African American Experience, or Spoken Word Poetry, or Journalism, for example.
Students are not all progressing to the same set of final exams either. Instead students can do courses that suit their aptitude, interests, and ambition - automotive tech, cosmetology, business lab, graphic design, and more, alongside required coursework in core subjects (English, maths, science, MFL, art, humanities) that can be taken at a level best suited to aptitude. Students aiming for university can taken honours/ higher level courses, and AP level courses. These courses offer final exams administered by outside bodies, operating on a national level. Students are continuously assessed in school in all subjects, every year, and the assessment is reflected in the grade point average.