Changes in big public systems often come glacially — that is, very slowly for a long while. Then external conditions shift just enough, and an entire ice sheet falls into the sea.

We'll discuss the science of glaciers another day. Today's topic is a long-cold idea that's thawing rapidly at the Legislature, to which I apply a dated abbreviation — K-14.

That label was in vogue among education visionaries in 1985, when Gov. Rudy Perpich pushed a skeptical, politically divided Legislature to allow high school juniors and seniors to enroll in college classes tuition-free and receive both high school and college credit for their exertion.

His innovation was called Postsecondary Enrollment Options, or PSEO, and it's been a fine thing for the relatively modest number of students who have taken advantage of it. Behind PSEO was a K-14 glimmer in Perpich's eye. He thought getting the educational equivalent of two years of college should become as commonplace in his "Brainpower State" as earning a high school diploma had been when he was growing up in Hibbing.

Today's education dreamers would surely call it "E-14," in deference to the importance of early education. Or they'd frame their notions as state Senate higher-ed chair Terri Bonoff does: "We need a streamlined approach to educating Minnesotans, from preschool through postsecondary learning all the way to Ph.D. I'd hate to limit it to 14 grades."

By whatever label, the 2015 Legislature is evincing a sudden burst of interest in more available and affordable postsecondary schooling for more — and younger — Minnesotans. Here's a probably incomplete list of ideas that have surfaced in the new legislative session's first two weeks:

• The big, pricey one: Free tuition at a community or technical college for any Minnesota high school graduate.

• Loan forgiveness for graduates in key fields, in exchange for a commitment to live and work in those fields in a region where they are most needed.

• Apprenticeships that combine work and college study in selected fields, financed at least in part by employers as well as taxpayers.

• More opportunities and encouragement for high school students to earn college credit right where they are.

See that ice sheet starting to slide? Ideas that high school and college are separate enterprises teaching discreet curricula — or that high school is for all and postsecondary education is for only some — are giving way. Something different is coming.

It's happening because the assumptions on which traditional high school and college notions were based no longer ring true. One premise was that a high school education would assure an adult self-sufficiency. Today it doesn't assure the ability to rent an apartment.

Another was what former Gov. Jesse Ventura used to say: "If you're smart enough to go to college, you're smart enough to figure out how to pay for it." That wasn't true even when he said it. Today, students pay more of the cost of "public" college education than taxpayers do. Seventy percent of Minnesota four-year college grads carry an average $31,000 student loan debt, the fifth-highest level in the nation and enough to rile an entire generation to demand change.

Then there's a looming labor shortage. Minnesota's working-age population has flatlined for the first time since at least the Great Depression, and it's forecast to shrink over the next two decades. Employers are already struggling to find the skilled workers they need. Job vacancies in the state are more numerous now than they've been since 2001 and are expected to increase, particularly in Greater Minnesota.

Filling those jobs will mean instilling more postsecondary skills in more Minnesotans, preferably without saddling them with more debt. One way or another, the ideas that have surfaced at the Legislature in the last two weeks aim to do just that.

The one I consider most promising harks back to 1985 and PSEO. Today, the term of art is "dual credit." It encompasses all the ways that high school students can do college-level learning and get college-level credit without paying tuition.

Academically gifted high school students have been able to do this for some time — witness Advanced Placement, International Baccalaureate, MnSCU's Concurrent Enrollment and the University of Minnesota's College in the Schools. There's the College Level Examination Program, awarding college credit via testing and featured in this newspaper last Sunday.

Those options have been around almost as long as PSEO. What could be next is a larger-scale integration of high school and both community and technical college curricula, for the benefit of a lot more students.

Long Prairie Grey Eagle (LPGE) High School is a pioneer at this, and well worth a legislative look. It launched what it calls "4 for 2" in 2010 — implying that students could do in two years what traditionally took four. LPGE's arrangement with Central Lakes College in Brainerd allowed 18 percent of its 2014 graduates to pick up both a high school diploma and an associate of arts degree at commencement. More than half of the LPGE class of '14 earned no-cost college credits that would have cost them an average of $4,000 had they waited to enroll in those Central Lakes classes after high school.

Coming next year at LPGE will be college-level technical and agriculture classes under Central Lakes auspices, taught by specially trained or certified high school faculty members, principal Paul Weinzeirl told me last week. He wants 4 for 2 to reach a larger share of the student body, including those who a generation ago might not have been deemed "college material."

Dual credit shouldn't be just for the academic top tier anymore, says Joe Nathan of the Center for School Change. He cites research showing that taking dual-credit courses may be most beneficial to the high school students now on the wrong side of the achievement gap, who are at risk of not graduating from high school. It turns out that discovering that one can do college work and cut college costs to boot fires one's ambition, boosting grades and chances of graduation.

Dual credit's potential to help close the achievement gap is one reason I'm keeping it handy in my K-14 file. Another is its relatively low cost. Sen. Greg Clausen, DFL-Apple Valley, a former high school principal, is carrying a bill to smooth the way for more districts to try versions of LPGE's program by paying for teacher training and boosting reimbursement for participation in the university's College in the Schools program. He anticipates a total price tag of a very affordable $10 million over two years.

It's also an idea that both Republicans and DFLers can love — as Perpich found 30 years ago, the last time Capitol power was shared by a GOP House and a DFL Senate. Rep. Sondra Erickson, the Republican chair of the House Education Innovation Committee, was as effusive in her praise for dual credit last week as was Sen. LeRoy Stumpf, the DFLer who's also the prime mover behind the bill for free two-year college tuition.

That's not to say dual credit is easy to expand. It rocks a lot of educational establishment boats. But educators ought to see as plainly as I do that their ice sheet is starting to slide. They'd be well-advised to figure out how to go with it.

Lori Sturdevant is a Star Tribune editorial writer and columnist. She is at