Three Dallas ISD schools rank highly on a list of the 15 most challenging high schools in the nation, according to a report by the Washington Post. In fact, two of them are in the top five.

First, the winners: The third-most challenging is the School for the Talented and Gifted at Yvonne A. Ewell Townview Center. No. 4 is the School of Science and Engineering at Yvonne A. Ewell Townview Center.

The Irma Lerma Rangel Young Women's Leadership School squeaks in at No. 15.

Dallas has the most schools in the top 15; three Arizona schools round out the top five. The report covered more than 2,300 campuses nationwide.

For its formula, the Post took the total number of college-level tests and divided that by the number of seniors who graduated. The tests include the Advanced Placement, International Baccalaureate and Advanced International Certificate of Education.

The formula is called the Challenge Index.

"The Challenge Index is designed to identify schools that have done the best job in persuading average students to take college-level courses and tests," they explain. "It does not work with schools that have no, or almost no, average students. We put those schools on our Public Elites list."

Some teachers are not impressed by the Post's annual survey. One called it "one of the most flawed and detrimental activities occurring in education today," charging that "administrators obsessed with getting their school recognized on these horrible lists are short-changing the kids."

A commenter named SuburbanMom suggests that the ranking system be given a more accurate title. "'Most challenging' is not accurate," she says. "How about 'The best at driving out the special ed students and bringing up the bottom?'"

The outcome is skewed by the fact that some parents must pay for placement tests while other students who qualify for free or reduced lunch take them for free or at a discounted rate. The survey also has at least one school on the list that has since been closed.

But Dallas ISD Superintendent Mike Miles took the city's showing as a positive sign. "This is further evidence of what we already know: Dallas ISD has some of the best students, teachers and schools in the country," he said.