The activist in this audio clip says that the poorer regular schools are expected to perform at the level of wealthier schools and magnet schools. If this is correct, then the pursuit of test scores is bound to fail.
The magnet school system, like the name says, is based on attracting the top students to go to specialized schools. To get into a magnet program, you need to have good grades. That usually correlates with high test scores. Within the LAUSD, nearly all students graduating from the magnet schools go to college.
If you have a population who are taking a test, and there's a normal distribution of scores, and then pull out a large number of the highest scores, the average score will drop. That's obvious.
It sounds like the below-average school is then being pushed to become average. That seems unfair -- all the best performers were pulled out of the school, so they now need to somehow get the more average students to do better?
So, the schools persevere, and actually manage to raise scores. if you look on the education websites, you will see a slow increase in performance. It has to be like squeezing Olympic performances out of mediocre players. But, as the population changes each year, even those gains are likely to be lost, because as students get better scores, they are going to apply for magnet programs, and leave the regular schools.
Furthermore, I don't know the situ in Chicago, but in LA, you have a thing called school choice, where many parents can choose between public high schools. This causes specialization and, to some degree, some schools become defacto academic magnets.
Combine this with the ability of families to move, which again causes some people to leave one school and go to a better scoring school, and I think demanding a non-random distribution of people in one school to rise to the average, when there are other schools within the area performing at above average, might be proven to be impossible.