No, I am not suggesting that there should not be variation and options within a school,nor do I think children should study for the same exams, there are many ways for a child to reach there best qualifications, but I do not think that specialisation should be built into a school. What happens to a child with a flair for languages who has to go to a school which specialises in science? A school that specialises does so at the cost of other subjects, if it doesn't it is not a specialist school. These schools may possibly work in large conurbations where there can be a wide range of them, though I have my doubts, but outside the big cities, you end up, as I have seen in my area a deeply rural school proudly boasting that it specialises in languages, which is fine for those with a gift for languages, but if a child's gifts are for maths or science they are going to be short changed. The nearest alternative school is 10 miles or more away and no transport will be supplied because the child and their parents chose not to go to te local school, or may have no alternative but to use the local school.
It is like going to a grammar school or being able to afford a house in the right catchment area, it is giving some children an advantage at the expense of others.