Poverty and MAP scores

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I was digging through city data's high school stats for a lot of the high schools in the metro, and for the majority of schools I looked at, the % of students with free/reduced lunch was within a few points of the % of students scoring below basic. A few really high poverty schools had higher below basic numbers, as did very affluent schools. MRH High, though, really punches above its weight for poor kids. (To some extent, so do Normandy and Riverview Gardens). Even though about half the school's students are free/reduced lunch, only about a quarter are below basic, and it has solid proficient numbers, too. Anyone know what makes this school so exceptional in this regard? By contrast LHW High has 3x as many below basic as free/reduced lunch.
Bumping this up. Anyone have insight as to why MRH is exceptional in terms of serving poorer students? Why Ladue seems to underdeliver with poorer students? At least by MAP score standards...
Maybe the special school district has something to do with this. Troubled students (arrests/drug possessions/behavior struggles) get sent to a probationary special school and they get removed from the general student population so they don't disrupt education for the rest.
^Students served by SSD are statistically part of whatever the local district is unless a student is profoundly physically or mentally disabled and attends one of the few SSD schools. SSD also doesn't operate schools for troubled students (i.e. alternative schools). MRH does operate an in-district alternative school for credit recovery, but it keeps those students' statistics with their peers at the high school, while Ladue does not operate an alternative school from what I know.

I have a few theories and speculations though:
1. Maplewood-Richmond Heights has a longer history of dealing with a significant low-income population, which is reflected in staffing choices and funding decisions that focus on the needs of these students (reading intervention specialists, club sponsorships, after-school programs, etc.).
2. Ladue's low-income population is *possibly* more transient than MRH because of housing insecurity. Ladue has a few apartment complexes near Lindbergh and Olive that probably contribute a significant share to its low-income population.
3. Depending on the years of the data, Ladue's low-income students might be voluntary transfer students, who might struggle with academics and present challenges for schools. (Ladue stopped accepting new students in 1999, so its last voluntary transfer students only graduated in the last year or so). MRH stopped participating before 1995, when it reached 25% black enrollment.
4. FRP lunch programs connect with Title 1, ESEA funding. Because MRH receives significant Title 1 funding, it is incentivized to encourage FRP lunch enrollment, while Ladue doesn't receive much federal funding and won't benefit as much from providing incentives to enroll. Thus Ladue might be unintentionally underreporting its low-income population. (I know this sounds far-fetched but there are different methods of encouraging kids to enroll, and some districts push FRP lunch way more than others.)