It’s only December, but the U.S. Department of Education is already thinking ahead to the 2015-16 assessment season in the spring—and it’s reminding states that they are still on the hook to do something about schools with low-testing participation rates under the Every Student Succeeds Act, the new version of the Elementary and Secondary Education Act. This is a crucial issue in an era where many parents are choosing to excuse their kids from standardized testing altogether.

The department sent a letter to state chiefs on Tuesday, outlining some of their options for how to deal with schools and districts that have high opt-out rates. It was signed by Ann Whalen, an advisor who is basically filling the job of the assistant secretary of elementary and secondary education.

Some background: When it comes to opt-outs, ESSA has a complex solution. It maintains a requirement in the previous version of ESEA, the much-maligned No Child Left Behind Act, that all schools test at least 95 percent of their students, both for the whole school, and for traditionally overlooked groups of students (English Language Learners, racial minorities, students in special education, kids in poverty). Under NCLB, though, schools that didn’t meet the 95 percent participation requirement were considered automatic failures—and that was true under the Obama administration’s waivers from the law, too. (That part of the NCLB law was never waived.)

Now, under ESSA, states must figure low testing participation into school ratings, but just how to do that is totally up to them. And states can continue to have laws affirming parents’ right to opt their students out of tests (as Oregon does).

This is the year of opt-outs, and no less than a dozen states—Rhode Island, Oregon, Wisconsin, Washington, Delaware, North Carolina, Idaho, New York, Colorado, California, Connecticut, and Maine, received letters from the U.S. Department flagging low-participation rates on the 2014-15 tests—statewide or at the district or subgroup level—and asking what they planned to do about it. The department is reviewing the information it got from states. So far, the administration has yet to take serious action (like withholding money) against a state with a high opt-out rate.

So what’s this letter about? It sounds like the department is reminding states that they must come up with some kind of a plan to address opt-outs in their accountability systems, even in this new ESSA universe. And if they don’t have some sort of a plan in place, they’ll risk federal sanctions.

And, in a preview of what guidance could look like now that ESSA is in place, the department gives a list of suggested actions states could take in response to low participation rates. These actions are all pretty meaningful, like withholding state and district aid, counting schools with low participation rates as non-proficient for accountability, or requiring districts and schools to come up with a plan to fix their participation rates.

The letter makes it clear that states can come up with their own solutions, though. So it’s possible a state could decide to do something a lot less serious than the options listed in the letter. But importantly, states’ opt-out actions would likely have to be consistent with their waiver plans, since waivers are still in effect through the end of the school year. (Plus, NCLB rules are still in effect for Title I money used this school year. More in this wonky post from Andrew.)

It’s too soon to say if a whole bunch of states will decide to make opt-out rates a pretty insignificant part of the picture for accountability once ESSA fully kicks in 2017-18, or if the department would be able to do much about it if they did, since many interpret ESSA as seriously paring back the department’s power over states. But maybe that’s something that will be cleared up as the Obama administration begins to regulate on the new law.