The logistics of reopening schools are daunting. Plans are full of details about which days kids will be eligible for, and pages and pages on preventing students and staffs from getting sick. What kind of limits will be placed on class sizes? What kind of cleaning? Will there be symptom checks or temperature screens? Masks for everyone or just adults?

These plans are important and necessary. But there is an issue that we aren’t talking enough about: What happens when there is a Covid-19 case in a school? The Centers for Disease Control and Prevention released its first guidelines on this topic last week, a long-overdue step toward getting schools to take this question seriously.

The instinct, I think, is to say we are working to make sure that doesn’t happen, and of course that is the goal. But that goal is unrealistic. Even if schools are successful at ensuring there is no Covid-19 spread in schools at all, there will still be cases arising from the community.

When we look at data from places with open schools — Sweden, for example — they are encouraging in showing that teaching is not a high-risk job. But that means that teachers are infected at the same rate as the rest of the community. Put bluntly: If 5 percent of adults in a community have Covid-19, we expect 5 percent of school employees to have it even if they are at no greater risk. This problem is largest in places that currently have high community spread, but it is a concern virtually anywhere.

Bottom line: When schools open, there will be cases. It is necessary to have a concrete plan for what will happen when this occurs.

It is worth pausing for a moment on why there is a reluctance to discuss this. In my view, it is because those who want to open are afraid that if they acknowledge there will be cases in schools, those who oppose opening will use that to argue schools are unsafe. Indeed, there are movements in Californiaand elsewhere saying that teachers should not return to the classroom until there are no new Covid-19 cases in the school community for 14 days. This is effectively a mandate to not open at all, possibly ever.

However, this concern should lead us to more transparency rather than less. Is it really better to trick people into opening, only to face panic and anger when there is a case? If we face the reality now, we are better able to prepare both emotionally and practically for what is inevitable.

Once you acknowledge the reality of cases in schools, it is clear that schools need a plan. The first part of this plan should recognize that schools should not open in person until cases of the virus in the surrounding areas are low. Putting a precise number on this is difficult, but at a minimum places that have locked down except for essential services should not open schools.

But for areas with low incidence, you still need a plan. And this plan needs at least two parts.

First, there needs to be what I’d call a micro plan: What happens when a single student or teacher in a classroom tests positive? Of course the affected person will need to remain home until cleared for a return to school. But what about the rest of the classroom, the rest of the floor, the rest of the school?

C.D.C. guidelines are fairly clear on what to do with the sick individual and what type of cleaning should be done. The guidance on the overall school approach is less specific. It suggests schools probably do not need to close for a single case, but beyond that, it pushes the decision largely onto schools and local health departments. It suggests a host of factors to consider — community transmission levels, contact levels and so on — but does not draw any bright lines. Even the suggestion of not closing after a single case is not definitive.

Schools are left to choose their own approaches. One extreme is to basically do nothing — just tell the sick student or teacher to stay home. The other extreme is to shut down the school for each case. If a school plans to do the latter, it may as well not open at all. There is an intermediate option: Close the classroom for a few days, clean it and reopen.