Pennsylvania Gov. Tom Corbett pauses as he concedes the election to Democratic candidate Tom Wolf on Nov. 4, 2014, in Pittsburgh. (Gene J. Puskar/ AP)

In recent days, education activists have become incensed with Rex Tillerson, the ExxonMobil chief executive, for remarks he made about public schools that were part of a story about the Common Core State Standards in Fortune magazine.

The article, titled “Business Gets Schooled” and written by Peter Elkind, describes how involved some leaders of big business entities were in promoting the Core standards in recent standards. It has long been known that Microsoft founder Bill Gates funded the creation and promotion of the Core through his foundation, but the extent of involvement by some other business leaders was not as well known.

[Dear Mr. Tillerson: ‘Please leave our children alone’]

After describing an unsuccessful effort by Gates to persuade Charles Koch to stop funding conservative groups opposing the Core, Elkind writes:

This extraordinary tête-à-tête is just one example of how the war over Common Core has personally engaged—and bedeviled—some of America’s most powerful business leaders. Hugely controversial, it has thrust executives into the uncomfortable intersection of business and politics.

In truth, Common Core might not exist without the corporate community. The nation’s business establishment has been clamoring for more rigorous education standards—ones that would apply across the entire nation — for years. It views them as desperately needed to prepare America’s future workforce and to bolster its global competitiveness. One measure of the deep involvement of corporate leaders: The Common Core standards were drafted by determining the skills that businesses (and colleges) need and then working backward to decide what students should learn.

Organizations such as the Business Roundtable have devoted considerable effort to the initiative. The education chair for that association of CEOs, Exxon Mobil XOM -0.97% chief Rex Tillerson, has played a particularly prominent role. A stern, commanding figure with an Old Testament glare and a chewy Texas drawl, Tillerson is an unlikely person to lead a campaign of persuasion. (Never a fan of the press, he declined to speak to Fortune for this article.)

Tillerson gave a number of speeches promoting the Core — and he lobbied policymakers in states to stick with the Core when some began to back away from the initiative after an uprising of critics from conservatives as well as others across the political spectrum.

Following is a letter Tillerson wrote in 2013 to then-Pennsylvania Gov. Tom Corbett (R), showing exactly how the business leader went about pushing for the Core. He reminds Corbett of the “significant operations” ExxonMobil has in Pennsylvania. The letter was also sent to the leaders of the state legislature, as well as to all members of the legislature’s committees.

Pennsylvania adopted the Common Core in 2010 before Corbett became governor (along with 44 other states that fully adopted the standards over a few years). Pennsylvania schools were given three years to fully adopt the standards, but a backlash against the Core began to grow and education leaders in the state persuaded Corbett in May 2013 to delay the full implementation of the Core. With a day of the delay announcement, Tillerson’s letter was sent to Corbett, who had supported the Core for some time before turning against it in 2014.

The Obama administration made state adoption of “common standards” — which essentially meant the Core — a factor in receiving Race to the Top money and obtaining a No Child Left Behind waiver, and it provided $360 million for the creation of new Core-aligned tests by two multi-state consortia. Pennsylvania had “joined” both of the consortia early on, but in 2013 withdrew from both and used its own standardized tests for accountability purposes.

In March 2014, Pennsylvania’s Board of Education repealed what was known as the Pennsylvania Common Core Standards, and adopted a new set of standards that were similar to the Core. In September 2014, Corbett ordered a review of the new standards to see if they were a significant enough departure from the earlier set.

Here is the letter: