When Florida decided last month to withdraw from a consortium of states that is writing tests for the new Common Core academic standards in math and reading, it sent a ripple of concern through the remaining states.

Florida’s departure from the Partnership for Assessment of Readiness for College and Careers (PARCC) came after two other states, Oklahoma and Georgia, decided to stay loosely connected to the consortium but not participate in its tests.

The loss of those three states means the fixed costs of creating new tests will be spread over fewer students, raising testing costs for the remaining states.

A study released Wednesday by Matthew M. Chingos at the Brookings Institution found that defections from the testing consortia will not significantly affect costs for remaining members.

“Because the consortia are so big and consist of such a huge number of students over which the fixed costs are spread, they can afford to lose quite a few members,” Chingos said, noting that Florida’s withdrawal will raise the per-pupil test costs by about 60 cents for the other states.

PARCC and the other group, Smarter Balanced Assessment Consortium (SBAC), estimate that their end-of-year test will cost $29.50 and $22.50 per student, respectively.

That created sticker shock for Georgia, which spends $12 per student for tests in math and reading. State officials have said they will try instead to write their own tests, perhaps joining with other states in a regional effort.

“Based on what we’ve seen so far, [defections won’t] knock the price up so much that it’s suddenly unaffordable for the rest of the states,” Chingos said, adding that even if half the current PARCC states left the group, it would increase testing costs by about $10 per student. “That’s less than the cost of a textbook.”

Still, if there were a “mass exodus” of states, either consortia could collapse, Chingos said. Seventeen states and the District belong to PARCC; 25 states belong to SBAC. The Obama administration awarded $330 million to the two groups to develop valid, reliable tests that could be administered and compared across state lines.

The new tests are supposed to measure critical thinking and be more engaging than fill-in-the-bubble multiple-choice tests widely despised by educators and students.

The Common Core standards, written by governors and state education officials in both parties and largely funded by the Bill and Melinda Gates Foundation, are designed to create consistent math and reading standards from kindergarten through 12th grade. Currently, academic standards vary widely among states, and that patchwork nature has been partly blamed for mediocre rankings of U.S. students in international comparisons.

The standards do not dictate curriculum, allowing states to decide what to teach.

States have been rolling out the standards in classrooms over the past several years and have committed to giving students new computerized tests based on the standards starting with the 2014-15 school year.

As school districts implement the standards, there has been rising opposition from progressives, many of whom object to standardized testing and are uncomfortable with the role of the Gates Foundation, and from tea party activists, who say the standards amount to a federal takeover of public schools.

Chingos said there’s no way that Georgia or other states can write their own high-quality tests at a lower cost.

“If they’re going to spend less than the consortia, they’re going to get a worse test,” he said. “There may be reasons why Georgia thinks the PARCC tests aren’t appropriate for Georgia, but there’s no way to get around the math here.”

Considering that the United States spends an average of $10,500 per pupil for education, $30 or $23 for tests doesn’t seem like much, he said.