I don't agree with that.
Hard work, strict discipline, willingness to kick out trouble makers, fail poorly performing students, eliminate the bigotry of low expectations, set high standards, expunge all this radical leftist "hate whitey" and other liberal PC bullish!t from the curriculum, stop social promotion, resist mommas showing up and complaining how little La'squisha is treated unfairly, administrations siding with the teachers and having their backs, reduce zero-value administrators by 90%, move control out of Washington to local school districts, stop taking Washington DC money, and a couple dozen other things CAN close the "achievement gap."
Unfortunately, none of that is possible in today's US of A.
OK, but the data is not on your side.