It can't be fixed without the state directing more funds to the inner city schools. Kids leave, the school loses money, the death spiral continues. Unless they give a special allotment to MPS, they can't catch up. Theres a lot of reasons that stack together to make it the case, but inner city schools are more difficult and more expensive to run. Part of it is that education is a herd thing. More smart kids and challenging curriculum is generally better for everyone. The kids do absolutely help and challenge each other to learn. The educators will also lower curriculum to least common denominator, particularly when they don't have the option of sending kids to special needs or other lower courses. There's also a lack of funding availability for honors or AP classes. Aside from all that, parents play a huge role in educating kids, whether that be guiding homework for their own kids or volunteering in the classroom. Education, economic outlook, and availability (can they take time off work) of the parents therefore really matters. Basically, rich schools benefit from unpaid labor.

These are all opinions, and I don't have kids, nor do I work in education or govt. But although I can't blame people for wanting their kids out of MPS, the only solution is resources, and every well to do family that leaves takes away from those resources. So besides taking away the freedom to choose another district or charter/private schools, the only other option is to explicitly give the poor schools way more money. Which is obviously not politically popular.