The headline "Unvaccinated, unmasked teacher infected more than half of students in class with Covid-19, CDC reports" would be rather more honest if it said "Teacher with Covid symptoms infects pupils". We know that vaccination does not prevent infection, so the fact that the teacher was unvaccinated is not a major point. The pupils were wearing masks (or were supposed to be) so we should not assume that if the teacher had worn one it would have made any difference.
The article cites the original source, https://www.cdc.gov/mmwr/volumes/70/wr/ ... mm7035e2_w
which shows a seating plan and says
all desks were separated by 6 ft. Students were seated in five rows; the attack rate in the two rows seated closest to the teacher’s desk was 80% (eight of 10) and was 28% (four of 14) in the three back rows (Fisher’s exact test; p = 0.036) (Figure 1).
On May 22, students in a another classroom, who differed in age by 3 years from the students in the class with the index case and who were also ineligible for vaccination began to experience symptoms. The two classrooms were separated by a large outdoor courtyard with lunch tables that were blocked off from use with yellow tape. All classrooms had portable high-efficiency particulate air filters and doors and windows were left open. Fourteen of 18 students in this separate grade received testing; six tests had positive results.
I think they need to check the airflow. Having open windows and air filtration is useless if the air still goes from teacher to student directly. One of their conclusions seems to miss the correct emphasis:
In addition to vaccination of eligible persons, implementation of and strict adherence to multipronged nonpharmaceutical prevention strategies including proper masking, routine testing, ventilation, and staying home while symptomatic are important to ensure safe school instruction.
The school correctly used three of the four strategies, yet failed. The emphasis should be on the one strategy that was not correctly implemented.