There is a stark gap in standardize test scores between more affluent and poor students in Colorado this year, as there is every year, in every single state and territory of the United States, in every significant sized city in the United States.
If there is any perfectly consistent result from educational psychology it is that socioeconomic test score gaps are always present and always large.
If a district, like Denver, shows rising test scores, it is almost always more likely that the socioeconomic demographics of the student body is changing, in Denver's case because it lured many middle class kids who left in the wake of desegregation back into the district from suburban and private schools. Improvements in educational outcomes are always always a second order effect.
It isn't impossible to secure high educational achievement (by any reasonable measure) from children with low socioeconomic backgrounds, but it is very hard. Maybe 5% of schools accomplish that and almost all of them require far more time in school than an ordinary public school and an emphasis on deeply changing the culture of their students to act like middle class kids.
These schools are also typically selective and can pick out higher IQ poor children. They also take advantage of the fact that poverty routinely causes children to not achieve their genetic potential in IQ. IQ is strongly hereditary, but it is more strongly hereditary in the middle class and up, when there are no significant environmental impediments to achieving peak IQ, than among the poor where environmental factors including exposure to lead and other pollutants, lack of parental stimulation, and other economic stressors prevent children from developing their natural cognitive abilities to the fullest.