Charter school students in Detroit outperformed their peers in the city’s conventional school district in 15 of the 18 subjects on state tests given to all Michigan public school students last spring.

Students in Detroit’s charter schools also scored higher than those in 18 chronically failing Detroit schools that in recent years were under a form of state receivership called the Education Achievement Authority.

All Detroit public schools, both charters and conventional public schools, performed below statewide averages on the state tests. The results of the tests, collectively called the M-STEP, are not adjusted to reflect the socioeconomic background of students. The M-STEP is given to students in grades three through eight, plus 11th-grade students.

While the gap between the share of students deemed “proficient” in Detroit charters and conventional district schools was occasionally within a couple of percentage points, it was often greater. This especially applied at the elementary and middle school levels, where performance gaps exceeded 10 points in some subject areas.

Compared to their peers in Detroit’s conventional district and the EAA, students in charter schools were about twice as proficient in English language arts, at 23.2 percent versus 11.4 percent. They also tested better in math, with 12.5 percent proficient versus 7.0 percent.

But students in Detroit’s conventional district and EAA schools earned better scores than charter students in fifth-grade social studies, 11th-grade social studies and 11th-grade science. Both charter school and conventional school students in Detroit scored well below state averages in all 18 recorded test subjects.

The M-STEP is Michigan’s annual statewide collection of standardized tests, meant to track student progress in English language arts, math, science, and social studies.

After taking the test, students are ranked as either “advanced,” “proficient,” “partially proficient” or “not proficient” in a subject. Students ranked as either advanced or proficient are deemed to have met state standards, while students ranked as either partially proficient or not proficient are deemed to have not met those standards.

Detroit currently has 64 charter schools operating within city limits and about 53 percent of all Detroit students attend a charter, according to the Michigan Association of Public School Academies.

Most Detroit students face additional challenges because of their socioeconomic background, as reflected by their eligibility for free or reduced-price lunches. Charter schools, especially, enroll such students: 78.1 percent of Detroit’s conventional district and EAA students are eligible, but 88.2 percent of charter school students qualify.

The state’s M-STEP results, however, do not take the socioeconomic status of students into account when rating student performance.

According to Ben DeGrow, who studies education policy for the Mackinac Center for Public Policy, this leads to misleading test results.

“Unfortunately, there’s a strong relationship between the rate of low-income students and lower raw test scores, because poorer children tend to bring more stress and less academic support to the classroom,” DeGrow said. “An apples-to-apples comparison of schools requires looking more at the value they are adding to students’ learning than just at the number of questions answered correctly.”

DeGrow added: “We ought to judge a school’s effectiveness by the gains it produces, not by the characteristics of students who come through the door.”

After multiple emails and a phone conversation about the M-STEP results, the Detroit Community Public School District chose not to comment.