Human beings love ranked lists. It has something to do with being a tribal species wired to respect pecking orders. I don’t entirely understand the science, but I do know that nobody paid much attention to my stories about high schools that failed to challenge students until I came up with a ranked list to dramatize the point.

Thirteen years later, has the latest Challenge Index rankings of American high schools, including a process that confuses some readers. We add more schools about a month after the list is first published. That means the rank your school had May 22 when the list first appeared is not the rank it has now on the High School Challenge.

Ranked lists of colleges, ice cream parlors and chiropractors are rarely updated in this way. College football rankings change every week because their won-loss records change. But the college-level test participation rates that determine our High School Challenge (moved this year from Newsweek to The Post) rankings stay the same (unless we have to fix an error). The reason most schools’ ranks go down is that more schools are inserted into the list. We are keeping our promise to recognize as many schools as possible that have reached our standard for giving high school students a bracing taste of college demands for critical thinking and deep analysis.

We depend on high schools themselves, and their districts, to fill out our forms so we can put them on the list. We have the email addresses of officials at several thousand schools that we think might meet our standard---at least as many college level tests as graduating seniors. But we don’t know for sure unless they tell us, or are in one of the few states that gather this data for all schools.

Public high school educators are busy people. Sometimes they don’t get the data to us in time, and panic when they see the list is published and they are not on it. This is really our fault. We didn’t remind them enough times. So we always update the list to make sure those stragglers make it.

With the additions we are making, the national Challenge Index list has nearly 2,000 schools for the first time. This is approximately 10 percent of all public high schools. We wish there were more, but most schools still restrict access to Advanced Placement, International Baccalaureate and other college-level programs, or don’t encourage average students heading for college to try them.

Your school’s rank may have gone down a bit, but it is still on a list recognizing its hard work preparing students for higher education. We want every school that qualifies for that honor to be there with you.