The percentage of Colorado students who dropped out of school rose slightly in the 2014-2015 school year, marking the first time in eight years the state’s dropout rate has increased, according to data released Thursday.

The dropout rate inched up from 2.4 percent in 2013-2014 to 2.5 percent in 2014-2015, a trend state education department officials described as disappointing and concerning.

While Colorado’s on-time high school graduation rate remained unchanged in 2015 — at 77.3 percent — minority students slightly narrowed the longstanding diploma gap separating them from their white peers. The percentage of minority students graduating on time topped 70 percent for the first time, rising 1.1 percentage points from 2014 to 70.3 percent.

The plateau in graduation rates comes after a run of of steady improvement; rates have climbed since 2010, when they were about 5 percentage points lower.

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The on-time graduation rate covers students who earned diplomas within four years of entering high school from the 8th grade. By another measure — high school completion rate, which takes into account students who received GEDs or “non-diploma” completion certificates — Colorado students took steps backward. That rate fell from 79.5 percent in 2014 to 78.8 percent in 2015.

The dropout rate reflects the percentage of all students enrolled in grades seven through 12 who leave school without transferring to another school during a single school year.

Rising dropouts a mystery

Judith Martinez, director of the education department’s Office of Dropout Prevention and Student Re-engagement, said state officials have yet to pinpoint reasons for the rising dropout rates or identify districts that may be driving it. The state does plan to analyze data to help root out why 500 more Colorado students dropped out in 2014-15 compared to 2013-14, she said.

“We know the cost of failure when a student drops out over a lifetime can be very high in terms of the cost to society,” Martinez said. “And it also has an impact on having a skilled and educated workforce. The ramifications of even one student dropping out is significant when it comes to impacting a community.”

Among the state’s largest school districts, there was no discernible pattern to rising and falling dropout rates:

 

Racial gaps familiar to other measures of achievement also can be seen in the dropout numbers:

 

In the 87,000-student Jefferson County School District, the dropout rate rose from 1.5 percent in 2013-2014 to 1.8 percent in 2014-2015. That translates to 699 dropouts in 2013-2014 and 766 in 2014-2015.

David Kollar, Jeffco’s director of dropout prevention and recovery, said his staff on the ground had a sense the numbers might be up, but couldn’t point to specific reasons. Through a partnership with a foundation and a nonprofit group, the district has focused the last couple of years on gathering data points to identify potential red flags with kids in school so intervention was possible before they dropped out, he said.

That meant the district wasn’t as focused on luring back students who’ve already dropped out, he said. But this year, the district has additional resources to help shore up that effort, Kollar said. He said Jeffco has made inroads reengaging with drop-outs who are older, a little off track and struggling to find work.

Graduation rates flat

Of the state’s districts and local education agencies, 144 — or 78 percent — had high school graduation rates of 80 percent or higher, a key state benchmark.

Among big urban districts, both Denver and Aurora saw their on-time graduation rates increase by two percentage points. DPS has seen student achievement and attendance grow as the forces of gentrification ripple through some neighborhoods. The graduation gains are encouraging to Aurora, which hasn’t experienced such demographic shifts and continues to struggle academically.

Graduation rates vary greatly by district and have a strong correlation to the racial and socioeconomic backgrounds of their student makeups. A look at on-time graduation rates in the state’s largest districts by enrollment:

 

And those same districts broken down by race:

Of the slightly narrowing racial diploma gap, Martinez said: “I think that’s encouraging, but more progress needs to be made.”

At a news conference Thursday, Denver Public Schools acting superintendent Susana Cordova said the state’s graduation rate data shows Colorado’s largest school district is making progress, “but we know we have a long way to go.”

DPS’s on-time graduation rate was 65 percent in 2015; eight years earlier, the figure was 39 percent. Cordova chalked up the progress to credit recovery efforts, intervening quickly when students are failing classes and the introduction of new “pathway schools,” or alternative schools for at-risk kids.

Other districts with large numbers of students who qualify for free and reduced-price lunches — a measure of poverty — also showed gains in graduation rates. One exception was Pueblo City Schools, which saw a dip:

 

The graduation rates also rose at seven of 10 school systems on the state’s accountability watch list, which are at risk of losing their accreditation for poor student achievement. Graduation rates are one critical measure, but it’s unclear how much of a difference the improvements will make. The state’s accountability clock is on a one-year pause.

Data: Colorado Department of Education, Graphics: Sarah Glen