The head of the Silicon Valley university at the forefront of the digital revolution in teaching and learning warned more than two years ago that “there’s a tsunami coming” in higher education. In hindsight, Stanford University President John L. Hennessy’s assessment could be seen as overstated.

With isolated exceptions, colleges and universities do not seem this fall to be in jeopardy of financial collapse. Experiments in offering free education through “massive open online courses,” or MOOCs, do not yet appear to be the market-disrupting force that some theorized they would be.

But Hennessy is taking a longer view. Ripples on the ocean’s surface far from shore, he contends, may yet signal a wave that will, eventually, rise and swamp the old college order.

The “vast majority of higher education institutions,” Hennessy argues, need to “transform to a more sustainable economic model.” The reason: Diminished state subsidies for public higher education and stagnant family income threaten to undercut the funding that supports schools with high fixed expenses.

Hennessy had used the tsunami metaphor in an interview with the New Yorker for an April 2012 article about Stanford’s role as the intellectual engine of Silicon Valley. (The school was not thrilled with the headline: “Get Rich U.”) Here are a couple takeaways from a conversation The Post had this year with Hennessy, beginning over a summer lunch in Washington and continuing through recent e-mails.

●Colleges must get real about attacking the problem of costs. “The change must come from a boost in productivity,” he said. And what is productivity? Simply put: Degrees per dollar. “Technology is the best shot we have at bending the cost curve by enhancing productivity,” he said.

Don’t fall for hype over free online courses. Don’t ignore them either. “There is a role for MOOCs both as a tool to educate educators and as the primary access method for students who have few other choices,” Hennessy said. “But they will not be the mainstay of U.S. higher ed.” MOOCs, he said, “are only a small portion of a much larger change: the more aggressive use of online technologies.”

That could mean that a college focuses on adaptive learning, using computers to tailor the pace and content of a lesson to individual needs. Or the college could use more interactive videos to deliver what in years past would have been conveyed through lectures, eliminating the stultifying effect when a professor acts as a “sage on the stage.”

Hennessy is hardly the only educator to make these points. But his views carry weight because of Stanford’s deep ties to the high-tech world. Indeed, some of its faculty started the well-known MOOC companies Coursera and Udacity. Also, Hennessy has had a notably long run at the helm of the elite university.

A professor of electrical engineering and computer science, Hennessy, now 62, became Stanford’s 10th president in fall 2000. He has served longer in the position than any of his peers whose schools rank among the top 10 on the U.S. News and World Report list of national universities.

Among leaders of top-50 universities, only four have held office longer: Shirley Ann Jackson, president of Rensselaer Polytechnic Institute since 1999; William P. Leahy, president of Boston College since 1996; Mark Stephen Wrighton, chancellor of Washington University in St. Louis since 1995; and Henry T. Yang, chancellor of the University of California at Santa Barbara since 1994.

In Hennessy’s time, Stanford has become the nation’s most selective university, admitting just one of every 20 students seeking undergraduate admission, and has risen to the top in annual fundraising. This week it reported receiving a staggering total of donations in the 2013-14 fiscal year: $928.5 million.

There have been occasional setbacks. In 2011, Stanford abruptly withdrew from a competition that then-New York Mayor Michael R. Bloomberg staged to choose a university to build a technology-focused campus on the city’s Roosevelt Island. Hennessy had poured enormous energy into the New York bid, hoping to make the California school, which opened in 1891, a truly bi-coastal university. But Cornell University won in partnership with Technion — Israel Institute of Technology. Stanford officials afterward said New York unfairly adjusted its demands in the competition — a contention the city denied.

“Our plan was ambitious, risky and expensive,” Hennessy told The Post. “In the end, the additional requirements imposed by the city were incompatible with our plan, which would take time and lots of resources. It would have been a big challenge to make it work and lots of hard work.”

If the plan had succeeded, Hennessy said, it would have given Stanford “a significant capability for the future, so I am disappointed in that sense.” But Hennessy said he is happily focused now on finding “other challenging high-impact projects.”

Like other university presidents, Hennessy is also focused on daily operational challenges. Federal data shows Stanford had more than 18,000 students last fall, about 7,000 of them undergraduates. Hennessy aims to grow the undergraduate total over the next few years, adding about 100 freshman slots in the fall of 2016 and more in ensuing years.

That might not make the university any less selective. But it would be bigger, with the caveat that Hennessy is aiming to keep a size manageable enough that students have a “shared experience that’s highly valuable.” Hennessy said he didn’t know whether the undergraduate limit should be 8,000, 9,000 or 10,000 students. “We just don’t have any idea,” he said.

Hennessy said campus safety takes up a significant amount of his time, especially with the emergence of sexual assault prevention as a national issue. There are also perennial questions about underage alcohol consumption and binge drinking.

Asked how he would counsel incoming students on these issues, Hennessy said he supports “affirmative consent,” a key concept in California’s new “Yes means Yes” law.

“When consent is truly affirmative, there are rarely misunderstandings,” Hennessy said. “If consent cannot be given, it is assault to assume it is given. And no one should be afraid to say no when they are unsure.

“If you drink alcohol, never drink so much that you don’t know where you are, who you are with, or how to get ‘home.’ Under such conditions, anyone can do things they later greatly regret. . . .

“Finally, promise to intervene when you see a troublesome situation; don’t be an uninvolved bystander. Help a friend when they need help doing the right thing.”

He also weighed in on federal policy.

Of President Obama’s plan to rate colleges, announced last year, Hennessy said the government should tread carefully. “The danger of not doing this right is the unintended consequences,” he said.

Graduation rates, he said, should considered through the prism of family income of students — preferably broken down by income quartiles or quintiles, not just the single criterion of whether a student is eligible for federal Pell grants. The nation, he said, also needs better information on graduation because the primary current metric is how many full-time, first-time students obtain degrees within six years. “You also need measures for the many part-time and nontraditional students,” he said.

Asked what two things he would seek if he could magically enable the federal government to take action to improve higher ed, Hennessy offered three.

First: “Hold schools accountable for outcomes” by requiring them to share some financial responsibility when former students default on loans or when Pell grant recipients don’t earn a degree. “If we don’t do something like this there is a danger that the federal loan and grant programs will collapse,” he said. “Of course, these programs need to be risk adjusted to be fair.”

Second: “Fix K-12 [schools] to get many more students college-ready.” Data from the ACT admission test, he said, show “that only one third of the students are fully college ready in English, math and science. ONE-THIRD! And far too many students are in remedial programs. This is the number one thing that government could do to improve college graduation rates. It’s very hard.”

Third: “Help low-income kids with a little college counseling.” Eight hours of preparation for the SAT or ACT tests can make a difference, he said, as well as an hour of personalized college counseling and a simplified financial aid system. “Too many talented low-income kids don’t get to college because the process is overwhelming. This is easy to fix.”

He acknowledged his second goal “is extremely difficult and may take a long time to accomplish.”