We education wonks have been arguing for years about the amount of testing in schools, even though we usually don’t know what we are talking about. It’s too much! It’s not! I don’t recall anyone providing any information about how much time is actually devoted to testing each year.

Lucky for us, the Boston-based nonprofit Teach Plus has gotten money from the Noyce and Bill and Melinda Gates foundations to answer the question. The researchers reported that administering tests takes much longer than school district officials say it does. Also, tests designed by school districts might be more time-wasting than the annual state tests we complain about most.

Authors Mark Teoh, Celine Coggins, Christine Guan and Tamara Hiller also examined a category of tests that bothers students more than adults. Read the report before your next PTA meeting. It’s only 24 pages long, and some of it is derived from data and interviews in Fairfax, Prince George’s and Howard counties, and the District.

The report’s first finding sounds like a victory for people like me who have argued that testing isn’t so bad. Across 12 urban districts, the authors concluded, the average amount of time students spend on state and district tests equaled only 1.7 percent of the school year “in third and seventh grade and substantially less in kindergarten.”

I am not celebrating. The report showed that figure is deceptive based on the testing calendars that school districts give to parents and the general public. The authors surveyed 300 teachers in Boston, Chicago, Indianapolis, Los Angeles, Memphis and the District who reported that the actual test administration time, based on their first-hand experience, is more than double that length.

In kindergarten, the school districts counted 2.3 hours a year of testing. The teachers said 7 hours. In third grade, the districts said 14.2 hours; the teachers said 27.7 hours. In seventh grade, where teachers and students had more experience with the process, the numbers were closer; districts reported 14.9 hours and teachers said 16.4 hours. Keep in mind this is only the time spent giving the test. The report did not assess the time spent preparing students for the test or analyzing the resulting data. That would be a much higher number.

That was not the report’s only troubling discovery. It found enormous differences among urban districts. A typical Denver student, for instance, “will have about 159.4 hours of math and English Language Arts testing by the time he/she finishes the eighth grade,” the report said. “By comparison the typical student in Chicago will have had just 53.8 hours of math and ELA testing. The difference of about 105 hours, after nine school years, amounts to about 19 instructional days, or almost four weeks of school.”

The District was somewhat below average in scheduled testing time compared to 11 other urban districts surveyed. But it had more testing time than the three suburban Washington districts surveyed. Nationally, suburban district schedules showed 1.3 percent of the school year spent in testing, compared to 1.7 percent in urban districts.

There was one mention of classroom and school tests, the most stressful to our children because they usually count on report cards. The researchers said these under-studied assessments “absorbed substantially more time than state- and district-mandated assessments.” Children rarely testify at hearings or write op-eds, so that issue is going nowhere.

District-designed tests take more time than state tests, the report concluded. Teachers nationwide complained, as D.C. teachers do, that district preliminary tests to help prepare students for annual tests often ask irrelevant questions and waste time. That is something local districts might be able to fix. Reducing the total time devoted to testing will not be so easy and might have unexpected consequences.