After months of quarantine and phased reopening, we now face another big decision: how to reopen schools across the state this fall. WGBH Morning Edition host Joe Mathieu spoke with Dr. William Hanage, an associate professor of epidemiology at Harvard's T.H. Chan School of Public Health, about the potential risks and benefits of getting kids back into classrooms. The transcript has been edited for clarity.

Joe Mathieu: Closing schools was a big deal when it happened. Months and months have passed, and officials are understandably perplexed about how to reopen them. No one can seem to agree.

Dr. William Hanage: Yeah, it's hugely difficult to understand how to handle schools in the pandemic. It's one of the biggest problems we face, because schools not only educate children — I know this for a fact, myself having two in public schools in Cambridge — but they also do a huge amount for our communities. They're real beating hearts. And so understanding how we're going to handle this going forward is one of the most crucial issues that we're facing as we're dealing with looking at the fall and the winter.

Mathieu: So this is reality in your home, as well. You can look at this from a couple of different perspectives. Do you feel like kids will be safe when they return? Is there a difference in age, for instance, that makes a difference to you, at least as a doctor, that we keep hearing about — that they have better immunity, that they obviously aren't experiencing the rates of infection of older people?

Hanage: Well, it's hard to know whether or not they are actually experiencing the same rates of infection because they are less severely affected. That means we have to [look] really hard to find cases because they don't present to us as obviously infected. You have to go out and look for asymptomatic cases of infection within kids.

They are obviously much less seriously affected, and when I'm talking about kids here, I mean the under-10s. Because there's a real difference between the younger age group and the older age group. I personally think it's really helpful to separate this out into questions about the risk to children, the risk to those who care for them — both educators and parents at home — and then the rest of the community as a whole, because it's the amount of community spread in the end that we're going to be really, really worried about.

Mathieu: A return to full-time, in-class education does not seem like a possibility, at least in the outset of the school year. Will it be until we find a vaccine?

Hanage: I think that it is possible that we might be able to do in-class education close to full-time for some age groups because, as I said, the under 10-year-old age group is much less likely to be affected badly, and there's also some evidence that they're less likely to transmit. Obviously, having a vaccine will make life a lot easier, but I think we have to decide what to prioritize. We have to decide which age groups we are going to be most able to educate with the lowest risk to the community, and then we also have to figure out exactly what the best way of doing that is. There are a lot of things on the table, and some of them are probably better than others.

Mathieu: What do you make of some of the precautions that we've heard about so far? School buses [are] a big issue; we haven't figured that out. But within classes, the idea of of spreading very young people out 6 to 10 feet and having them keep their masks on all day has a lot of parents snickering.

Hanage: Yes, I can understand that. But if you look at the sort of places which have managed to do this well, which include various countries like Denmark and Finland, you can see that it is possible to reopen schools for younger kids and there's actually very little evidence of transmission. And I'll return to that because of the fact that there is a very good comparison between Sweden and Finland.

The thing I would like to mention now is that one of the things on the table is the possibility of a hybrid model in which people spend some time at school and in some remote learning. Now, the difficulty with that from an epidemiological point of view is the number of contacts which get generated. So if kids are in school two days a week and then the other three days a week they are at home, the parents are probably going to end up having to seek child care from somewhere else. That means the child is making a new contact they would not have made otherwise, and that just provides another chance for the child to become infected and then bring it into the school.

So I actually think that the hybrid model is probably among the worst that we could be putting forward, if our goal is to stop the virus getting into schools.

Mathieu: Doctor, you're talking about what's the most likely scenario.

Hanage: Unfortunately, this is so. My personal view is that it would be more sensible to consider prioritizing the younger age groups for as much education as possible. And in particular, there are some kids who may be needing more education than others.

Mathieu: There are a lot of elements here, doctor, but I've heard you mention in the past that when it came to the phased reopenings, that schools should have been considered a priority when we looked at all businesses instead of being the last thing that we get to.

Hanage: Yes, indeed. When we think about reopening, I think that's thinking about it the wrong way.

What we should be thinking about is pandemic management. What that means is that there's a level of transmission that we are comfortable with, and that might be none or it might be a certain number of cases per day. And then we have to figure out how many contacts we're going to allow the virus, which are going to be compatible with that.

Now reopening schools, doing anything which allows the virus a route to transmit, will increase the opportunities it has for transmission. That's really simple. It's epidemiology, it's not rocket science. So we have to figure out how many of those we're going to allow it. And I think that schools, as I said, are such an important part of our communities that we should be trying to prioritize them. Which means, unfortunately, that some other parts of our society are going to have to take the hit in terms of limiting contacts.

So right now, you look at Massachusetts, we've actually got an estimate of the reproduction number right now, which is the number of people who got infected by a single case at the moment — around about one, which means it's bubbling along. It's not going up, [but] it's not done down, unfortunately. But we're going to be continuing to see transmission continuously at the moment.

But in the fall, we're going to be seeing a number of things changing. That includes colleges, some of them doing in-person teaching. We're going to be seeing schools reopening. We're going to be seeing more opportunities for transmission. And crucially, in the fall and the winter, it's going to be [more] difficult to meet up outside. And we need to be prepared for that. We need to be ready to take action promptly in order to prevent the kind of damaging surge that we saw in the spring and which other parts of the country are seeing right now.

Some of that may include, once again, having to shut the schools. I think it is of great importance for teachers to be able to bond with the students they're going to be teaching. It's going to be really hard for them to do that online. If community transmission early on is sufficiently low, I do hope that it's going to be possible for teachers to actually meet with their students in person for at least enough time they can form a bond, because even though we can anticipate that there's going to be more transmission and schools may have to close again, those few weeks may end up being vital.