To the uninitiated, they might not seem like major offenses: a school principal deciding not to fill empty seats midyear for fear of attracting too many “less capable” students, or another principal sitting down with the family of a new student to see if the child was the right “fit for our institution.”

In the context of New Orleans public schools, however, these are no-no’s. Schools here operate without traditional attendance zones, so they compete with one another for students from across the city. And most are independent charter schools, which can be shut down if they don’t improve academic results beyond a certain point.

Any sign that schools might try to make life easier for themselves or boost their test scores by accepting only certain children would constitute what’s known in public education as “creaming” and in some cases might violate state policy.

But that’s apparently what at least some schools in New Orleans have done in past years, responding to competitive pressures and the need to lift test scores, according to a study released Thursday by Tulane University’s Education Research Alliance.

The study, conducted by Huriya Jabbar, of the University of Texas at Austin, drew on interviews done in 2012 and 2013 with more than 70 individuals from 30 schools. The goal was to see exactly how people running schools in New Orleans dealt with competition for students, which is sometimes cited as one of the drivers behind rising test scores and falling dropout rates in the years since Hurricane Katrina.

What she found, Jabbar said, was that “schools do not always respond to competition in a way that policymakers hoped.”

Just 10 of the randomly selected schools she queried told Jabbar that they dealt with competitive pressures by trying to improve academics or instruction. About half said they tried to set themselves apart somehow, through extracurricular activities or other strategies. Most of them — 25 — spent resources on advertising and marketing.

And 10 of them did some type of “screening” that could have left them with higher-performing students, although the number drops to eight if you remove from the list a magnet school with explicit entrance requirements and a French immersion program.

Underscoring the confusion that the city’s unique school system still inspires — even among educators — Jabbar reported that many principals acknowledged these types of screening practices “matter-of-factly,” apparently unaware they might be breaking any rules.

“This study does not aim to judge the actions of the principals,” Jabbar said in an email. “Most of these school leaders are working hard to provide a good education to students, but they are facing a complicated set of incentives and pressures.”

Drawing any specific policy conclusions for New Orleans may be complicated, however. That’s, in part, because schools here have attracted these types of accusations for years, and in 2012 — just as the ERA study was being conducted — state officials imposed a new centralized process that took enrollment decisions out of the hands of school leaders.

In a briefing with reporters this week, Jabbar and ERA Director Douglas Harris acknowledged that recent improvements in the so-called OneApp system would probably help prevent future abuses.

Another complicating factor is that these practices apparently were not confined to charter schools or to the Recovery School District, the state agency whose controversial takeover of New Orleans schools after Katrina has made it a source of constant debate.

Without naming individual schools, Jabbar said the eight schools in question included both charter and traditional schools. Five of them fell under the RSD. Three were under the Orleans Parish School Board, which was left with a handful of schools after the storm.

There are also disagreements about whether “school choice” is really supposed to improve the quality of schools in the first place — an idea the study purports to cast doubt on by highlighting “screening” and the money that schools spend on marketing instead of classrooms.

The decision to eliminate attendance zones in New Orleans is also sometimes cast as simply giving students a way to escape failing schools in their neighborhoods, which might otherwise be their only option.

Michael Stone, of New Schools for New Orleans, a group at the forefront of the charter movement, argues that is actually the prevailing view here. He said giving schools autonomy and holding them to a certain standard is what is driving improvements, rather than competition.

“I don’t think I know a single person working in public education in New Orleans who would say that competition for students will drive quality,” Stone said in an email. “Maybe it’s not perfect for schools to spend some portion of their resources on marketing, but that’s the trade-off we make to ensure that kids aren’t locked into dropout factories in their neighborhoods.”

Whatever the case, ERA’s report does provide a telling snapshot of school practices in 2012 and 2013, and it could be read as a cautionary note for other urban districts mulling open-enrollment policies.

One principal explained frankly why he felt he should leave seats at his school open rather than advertise to fill them.

“We know the more we advertise and push the fact that we have openings, the more less-capable students we get,” he said. “So yeah, I’m about 100 kids below what we were targeting, but it’s a double-edged sword. Do I want 100 kids in the building who aren’t in school?”

Another principal described trying to attract certain families: “We’ve done invite-only open houses, where we target specific types of parents, and we say, ‘Hey, we really love you as a parent and we want you to bring another parent who’s like you.’ ”

A third principal complained that with the OneApp coming, she wouldn’t be able to interview families before they enroll students anymore.

“On OneApp, the children choose you,” she said. “Previously, we were able to do interviews and just see if the family fit for our institution. … Some students may want to come … but will not be prepared for the expectations of the school.”