We’ve been keeping an eye on the reported cases coming out of our kids’ school district, Leander ISD. Living in Texas, the mitigation steps taken to contain the spread of COVID-19 is minimal:
- an unenforced mask mandate
- no social distancing
- no pods / containment strategies for limiting contact in secondary school
- no staggered bell schedules to reduce hallway crowding
- no outside lunch options available for increased distancing
The relative lack of mitigation efforts alarmed us, so we started taking a closer look at what data was available from the district that we could use to better inform ourselves of what was going on in our school, and the schools around us.
available weekly data
cases as reported by the district
Leander ISD posts case data in a cumulative weekly time series view. I’ve combined 2020 through 2022 data in a vertically oriented bar chart. This series is reverse sorted, with the most recent time period at the top. The plot illustrates the magnitude of the progression of infections moving from alpha to delta to omicron, and with the reduction in preventative measures, the overall increase in the severity of the outbreaks.
Omicron’s impact with no mitigation strategies is truly astounding relative to prior waves. Though the case percentages relative to the student population remain low, anecdotal reports are that 20-30% of students are out sick at the peak of omicron.
cases by grade
An interesting view is case load as a function of grade level. After the first 3 weeks of classes the 5th and 6th grade levels clearly show a distinct concentration of cases relative to the rest of the grade levels.
It is interesting that 5th is the last grade level in elementary school and 6th is the first in middle school, so these cohorts should not have significant contact within school.
(scroll left to right for daily heat maps)
cases by school
(scroll left to right for daily heat maps)
cases by postal code
Leander ISD spans a large geographic distribution that includes Leander TX, sections of Cedar Park TX, and sections of Austin TX. We can aggregate case data across postal codes, which shows where case concentrations are as a function of location. We see that case loads are much higher in the Leander and Cedar Park postal codes:
(scroll left to right for daily heat maps)
For perspective, here is a zip code map for LISD:
impact of masks and distancing
What can we infer from the available data on the impact of masking and distancing on case arrival rates? We can pull in data from 2020-2021 for LISD’s case rate when a significant portion of the student base was virtual (fall 2020) versus returning (spring 2020). Masks were required for in-person learning in 2020-2021.
The significant change was moving back to full capacity / no distancing in 2021-2022, and moving to masks optional. (NOTE: LISD maintains they have a mask mandate in place with an opt-out policy, but the opt-out is simply not enforced. Anecdotal evidence points to ~20% to 30% of students actually wear masks, versus 10% to 20% that have filled out the opt outs.)
We don’t have as robust of a view in case loads for 2020-2021 that are presented above, but the weekly statistics aggregated across the district are useful for comparing the difference in containment approaches year over year. In summary:
| 2020-2021 | 2021-2022 |
|---|---|
| begins virtual | limited virtual option |
| reduced student capacity | full capacity |
| mask mandate enforced | mask optional |
| social distancing in place | no social distancing in place |
| student movement reduced / use of pods | full student movement / classroom changing |
The key differences here are no masks, no distancing, and little limitation or alteration of schedules to minimize contact between cohorts.
Here is an impact based on the number of cases per day (average across a 7 day week) per 100,000 as of September 8 2021:
| median | maximum | |
|---|---|---|
| 2020-2021 | 1.4 | 8.1 |
| 2021-2022 | 13.1 | 22.2 |
| zero mitigation percent increase | 855% | 175% |
| zero mitigation multiplier (e.g. “x times greater”) | 9.5x | 2.7x |
This summary looks at the median daily rate per 100k for a given week for the two school years (2021-2022 is in progress).
The case rate per 100k is 9.5 times greater than the median values seen in the prior year when social distancing and mask mandates were enforced.
Even at their peak, the 2021-2022 school year is already 2.7 times greater than anything observed in the prior school year.