Idaho’s graduation math has been convoluted at best.

For years, the state’s political and business leaders took comfort in numbers that suggested Idaho had one of the nation’s highest graduation rates.

Then Idaho changed the way it calculated its graduation rate — tracking students over a four-year period. For years, that’s been the standard practice nationally, and in most other states.

When Idaho switched to apples-to-apples math, the state began accounting for students who left high school over four years, not just in senior year. The results, not surprisingly, was a dropoff in Idaho’s numbers. In 2013-14, Idaho’s graduation rate came in at No. 41. In the 2014-15 numbers, released Monday, Idaho’s ranking improved to No. 39.

Analyzing the graduation numbers is no less simple at the national level.

Emily Richmond of the Education Writers Association posted a must-read blog Monday, running through some of the pitfalls in analyzing the national graduation numbers.

Yes, the nation’s graduation rate reached a record 83.2 percent, with improvements across all demographics.

But as Richmond points out, achievement gaps still persist. Richmond’s blog also links to other education writers who focused on other lingering questions — including, for instance, the difference between graduation and college- or career-readiness.

The lesson: The graduation rate is a high-profile metric used to compare schools and states. But it isn’t a flawless metric.