"If you have a forest of barriers in a classroom, it’s going to interfere with proper ventilation of that room... Everybody’s aerosols are going to be trapped and stuck there..."

"... and building up, and they will end up spreading beyond your own desk.... One way to think about plastic barriers is that they are good for blocking things like spitballs but ineffective for things like cigarette smoke. The smoke simply drifts around them, so they will give the person on the other side a little more time before being exposed to the smoke. Meanwhile, people on the same side with the smoker will be exposed to more smoke, since the barriers trap it on that side until it has a chance to mix throughout the space."

Said Linsey Marr, "professor of civil and environmental engineering at Virginia Tech and one of the world’s leading experts on viral transmission," quoted in "Those Anti-Covid Plastic Barriers Probably Don’t Help and May Make Things Worse/Clear barriers have sprung up at restaurants, nail salons and school classrooms, but most of the time, they do little to stop the spread of the coronavirus" (NYT).