In Baltimore, and everywhere else, raising the minimum wage, offering free daycare & preschool, and improving the social services that prevent many low income kids from learning outside of the school (and parents from supporting them) is what will make the real difference. But, at least half of this country is opposed to spending money on those sorts of things because the "I got mine" attitude is more pervasive than "What's good for my neighbor is what's good for me".
For example in a poor area with more crime a child may need after school programs, which cost more money, to keep kids out of trouble.
Urban school districts in the US are disproportionately in old buildings that have high maintenance costs, low efficiency for utilities, and have all sorts of problems that need remediation, like lead or asbestos. There is generally no capex money to replace these buildings, and even if there was, finding a suitable property in an urban area is pretty difficult, since schools are big.