It’s a time-honored balancing act of public education: autonomy vs. consistency, local control and local choices vs. what politicians like to sneer at as “one size fits all.”

But education is a little like money. (In many obvious ways, education is money.) To wit, if there’s no common currency, there’s no coherence. A dollar might have different buying power in New York City from what it has in (Georgia), but at least there’s a comprehensible basis for comparison.

Unless a K-12 public school education means substantially the same thing in Idaho that it means in Georgia and the Carolinas and Arizona, standards are a veritable Tower of Babel.

Georgia, like other states, has been trying to achieve the proper balance for years. The latest approach is the Common Core curriculum, which all but three states have adopted as a measuring stick of student achievement. In order for that curriculum to produce consistent results, of course, there needs to be a common basis for assessment.

And that, state Superintendent John Barge said last week, is a big hurdle right now. Not because of the approach — Georgia is one of the 47 states to adopt it — but because of the price.

In an address to the annual State of Education conference at the University of Georgia, Barge put the cost of Common Core testing at more than four times what Georgia pays now, according to a report in the Athens Banner Herald. Barge said the state today pays about $5 per student for testing; Common Core would cost up to $22 per student.

In a state economy that struggles to find $730,000 to keep the Georgia Archives open, $22 for each of more than 1.6 million students is some heavy arithmetic.

“That’s very expensive for the state of Georgia,” Barge said, in what has to be considered quite an understatement.

Part of the high cost is attributable to the technology of the tests, which runs into another problem: the digital divide. These tests are designed to be computer based and interactive, yet Barge said the technical specifics aren’t yet clear: “We don’t know the appropriate bandwidth we need to have at each school.”

In some cases — and not just in Georgia but almost surely across the country — that’s irrelevant, because many schools are in places with no wireless access anyway.

At least there seems to be time available to get this sorted out and, ideally, a lot less expensive.

The new system is supposed to be in place by the 2014-15 school year, but the contract for the testing system is being challenged by a competitor.

“It’s going to take a lot longer than 2014-2015,” Barge told his audience. Another understatement.