Streaming works well if it is done well. If it's not done well then it is just as crap as any other system that isn't implemented well.
I went to a modern comprehensive late '70s, early '80s; it had five years each with ~200 pupils in six forms. Streaming was by subject: you could be in top set for maths and bottom set for English, though this was unusual. In the first two years each year was split into two, the latter three years the streaming was done across the whole year. At the end of each year each stream in each subject was reassessed; it was also possible, though not often, to change stream mid-year.
I think I was streamed well; I certainly followed pretty much everything I was taught. Most of my fellow class members seemed to do so too after not too much explanation.
no subject
I went to a modern comprehensive late '70s, early '80s; it had five years each with ~200 pupils in six forms. Streaming was by subject: you could be in top set for maths and bottom set for English, though this was unusual. In the first two years each year was split into two, the latter three years the streaming was done across the whole year. At the end of each year each stream in each subject was reassessed; it was also possible, though not often, to change stream mid-year.
I think I was streamed well; I certainly followed pretty much everything I was taught. Most of my fellow class members seemed to do so too after not too much explanation.