If you take the lowest performing kids from any school district and put them in a separate school, I promise you'll see the same results. They are starting way behind in ability, especially reading level, which is the cornerstone of success in education. All of them. Some of the kids arrive there 2-3 grade levels behind. So even though a large percentage of their scores might improve over the course of the year, they still "fail" according to the standardized tests. A 5th grader comes to them at a 3rd grade reading level, improves to a 4th grade reading level, but still fails the test because they're still behind. It is why nobody should look at standardized test results as the primary indicator for school success. It's much more complex than that, and it's why the large majority of educators dislike the current standardized test system.
If people can't see how graduating kids and sending kids to college that would probably end up on the streets otherwise if it wasn't for the school isn't helping the community, I'm not sure what to tell them.