Last week, when we took a  close look at achievement gaps at Denver’s East High School, we reported that “the breadth of East’s TCAP [the state test] gaps may be explained in part by how high-achieving East’s top students are,” because minority students also perform better on TCAPs than their counterparts across Denver Public Schools.

But after an astute reader prompted us to take a closer look at data, we found some interesting nuggets that show what achievement gaps look like across the city and suggest some interesting explanations we might have missed in the original story.

First, East has fewer low-income students (as measured by eligibility for free and reduced-cost meals) across all races and ethnicities than other Denver comprehensive high schools. And that may do more to explain why the performance of all groups of students is higher at East than in DPS overall.

Just 8 percent of East’s white test-taking students (ninth and tenth graders) are low-income. That’s compared to 27 percent at all other DPS high schools. While 86 percent of Latino students at other Denver high schools are low-income, at East the percentage is much lower –62 percent. And 70 percent of East’s African American students are low income, compared to 80 percent at the district’s other high schools.

Furthermore, the ratio of non-poor to poor white students at East is much wider than at other Denver high schools. And while the proportion of non-poor to poor black and Latino students is also wider than at other high schools, it’s by a much narrower margin. So the larger achievement gaps could be explained in part by how many fewer low-income white students there are compared to low-income Latino and African-American students.

It’s also notable that two of  the three Denver high schools that have higher-performing white students than East also have significantly smaller achievement gaps by race.

The two schools are distinct from East in that one, DSST’s Stapleton high school, is a charter school that students choose to attend rather than being assigned by residence. The other, Denver School of the Arts, a selective admissions magnet. And both have lower percentages of low-income students than does East. Still, it’s worth noting the difference in gaps.

DSST’s Stapleton charter high school had an average TCAP proficiency among white students of 93.6 percent in 2013, compared to East’s 81.2 percent.  Yet its proficiency gaps between white and black students was 21.7 percent, compared to East’s 45.3 percent, and its white-Latino gap was 18 percent compared to East’s 36.9 percent.

And while a smaller share of DSST Stapleton’s black students are low-income, more of its Latino students are. Among black students, 54 percent qualify for subsidized lunches, compared to East’s 70 percent. Among Latino students, however, 79 percent qualified for subsidized lunches, compared to 62 percent at East.

At Denver School of the Arts, a magnet school that requires an audition for admission, the average white proficiency rate was 81.3 percent, a tenth of a percentage point higher than East’s. Its black-white achievement gap was also far lower than East’s — 29.6 percent compared to 45.3 percent. And its Latino-white gap was 10.8 percent, compared to East’s 36.9 percent.

But the school also had fewer than 16 students in any racial/ethnic group eligible for subsidized lunches, meaning its poverty rate among all groups is very low.

The school with gaps that top East’s is George Washington High School, where a selective admission International Baccalureate program largely walls off that high-performing student population for core academic classes from the rest of the school. At GW, the black-white gap is 56.2 percent and the Latino-white gap is 45.4 percent.

It’s also worth noting that these gap trends don’t change much when you look only at each school’s non- free and reduced lunch eligible students of all races. George Washington still has the widest gaps, followed, in order by East, Denver School of the Arts, and DSST.