Having grown in Poland, I have to say I was very lucky to be born in 1985 which was the cut-off year for the reformed educational system. I managed to escape it. It is widely agreed that the system brought nothing but deterioration in the level of education students receive pre-univeristy, esp. in maths/physics/chemistry. So much so that when I was still studying in Poland, I often heard that "new" students are at a level comparable to "old" part-time students.
> He decided to keep all Polish children in the same schools until they were 16, delaying the moment when some would have entered vocational tracks.
This is misleading. First of all, education is obligatory until one is 18 years old in Poland. There is no such thing as dropping out of school before that age.
The previous educational system was two-tier, with primary school lasting until 15 years old, and high school lasting the remainder 4 years (5 years for vocational high school, AFAIR). There were no electives in primary school, so the first real sorting of students based on ability was taking place at entrance exams to high schools (which had no obligation to accept a student based on their geographical location). What the reform implemented is it created a third tier in between primary (shortened by 2 years) and high schools (shortened by 1 year), the gymnasium. Gymnasiums do not have the sorting ability of high schools. With the end result being that what high schools were previously struggling to teach in 4 years now they have to condense into 3 years. So a lot of things are left out now. Plus the students they get at entry are also of lower quality -- I remember browsing through the first set of chemistry textbooks for gymnasium and being shocked that what the "old" system primary school students had to cover in two years was supposed to be covered in a lesser form in 3 years of gymnasium. So yes, the reform postponed the division of students into university/vocational tracks by one year, but at the cost of overall quality of education.