ACT became the largest purveyor of college admissions tests in the U.S. in 2012, passing the SAT. Fifty-four percent of 2013 high school graduates took the ACT sometime during high school.

An annual national study by ACT concluded that, in 2013, only 26 percent of all ACT-tested high school graduates met ACTs College Readiness Benchmarks in English, math, reading and science.

ACT defines college and career readiness as "the acquisition of the knowledge and skills a student needs to enroll and succeed in credit-bearing first-year courses at a postsecondary institution (such as a two- or four-year college, trade school, or technical school) without the need for remediation."

ACT determines if students are college-ready with empirically derived benchmarks on ACT subject area tests. The test benchmarks are indicative of whether a student has a 50 percent chance of obtaining a B or higher or about a 75 percent chance of obtaining a C or higher in corresponding credit-bearing first-year college courses.

These college courses include English composition, college algebra, introductory social science courses, and biology. Between 2009 and 2013 average scores on the ACT dropped from 21.1 to 20.9.

While 43 percent of Asians taking the ACT met all four benchmarks, only 5 percent of African-American and 14 percent of Hispanic-American students did. Thirty-three percent of white students were considered college ready in the four areas.

Delving a bit deeper, the ACT benchmark numbers paint an even bleaker picture. After all, the students taking the ACT are students who are likely to be applying to colleges, particularly competitive colleges that require an admission test.

While some of the graduating seniors who did not take the ACT took the SAT only, the majority of low-performing students will not have taken any admission test. Those students, on average, would almost certainly have performed even more poorly on the ACT, further skewing the numbers downward.

The big problem is that none of this is really news. ACT has collected and reported data on students' academic readiness for college since 1959 and the numbers are strikingly and depressingly similar. The vast majority of students attending, or who are hoping to attend, postsecondary schools this fall are inadequately prepared to succeed there.

The College Board, the nonprofit membership organization of schools and colleges that owns the SAT, reported last year that merely 43 percent of test-takers met their benchmark score in 2012, indicating a 65 percent likelihood they can achieve a B-minus average during the first year of college. That score was unchanged from 2011.

According to a report from the National Assessment of Educational Progress released in June, elementary and middle school students are scoring higher in reading and mathematics than 40 years ago, but " (A)verage reading and mathematics scores in 2012 for 17-year-olds were not significantly different from scores in the first assessment year," which was 1971.

The data paints a clear picture. We are failing to make sure that our nation's high school graduates are adequately educated. Until we can ensure that those graduates are prepared to tackle the challenges of postsecondary education, we should stop handing out high school diplomas that imply that they are.

Patrick Mattimore was a high schoolteacher in the Bay Area for many years and is an adjunct professor of law in the Temple University/Tsinghua University LLM program in Beijing, China.