Many of the “top” schools in Spain use a slightly deceptive strategy to get high ratings. They begin primero with a large number students and weed out the worst ones as the grades progress. By the time the students reach the last two years, all the average or below average students have left, leaving a somewhat elite final class whose main purpose is to do very well on their exams and make the school look good. Even students that are above average will in many cases leave for another school in the last two years, since top grades in an easy school looks better than being below average in a top school.
The bottom line is that it’s not clear that going to these elite school really benefits gifted children, since the children that survive to the end might have been very successful in any setting.