What the prediction claimed

Sacks predicted that in the 2020–21 school year:

1. Many schools would reopen with elaborate mitigation plans (pods, reduced class sizes, etc.).
2. As soon as there was one COVID case in a school community, they would quickly shut down again.
3. This would make the year a broadly chaotic, stop‑start experience for families.

What actually happened in U.S. K‑12 schools

1. Reopening with elaborate plans – partly right
   • Districts did create detailed reopening plans with cohorts, small classes, staggered schedules, and other mitigation measures—examples include Detroit’s 2020–21 plan (class-size caps, staggered starts, distancing, etc.) and similar “small cohort” models in New York and other districts. (fox2detroit.com)
   • However, on the first day of the 2020–21 school year, almost half of tracked U.S. districts opened fully remote, and among the 100 largest districts, 74% chose remote‑only—meaning large numbers of students never “went back” in the fall at all. (edweek.org)

2. Do schools that reopen shut after a single case? Mostly no
   • A national CDC analysis found that from late July 2020 through June 2021, about 16,890 schools experienced 19,273 COVID‑related unplanned closures. The U.S. has roughly 130,000 K‑12 schools, so only about 13% of schools had any COVID‑closure that year, and most of those had just one closure; only 12.1% of affected schools closed 2–7 times. (wwwnc.cdc.gov)
   • In Florida—one of the states that fully reopened early—CDC data show tens of thousands of school‑related student and staff cases, but only 28 schools in 12 counties closed temporarily in fall 2020, with a median closure of four days, plus partial classroom closures in 226 schools. This indicates that most schools did not automatically close the whole building after the first detected case. (cdc.gov)
   • Nationally, closures were generally attributed to clusters of cases, broader community transmission, or state/local mandates—not a hair‑trigger response to a single infection. (wwwnc.cdc.gov)

3. Was the year dominated by stop‑start chaos? Mixed, not universal
   • Many large urban districts (e.g., in Chicago, Philadelphia, Boston, San Diego, D.C.) delayed reopening and stayed remote for much of the year, rather than reopening and then immediately shutting again. Reporting in late 2020 describes these districts repeatedly postponing initial reopening plans as community cases rose, rather than cycling in and out after opening. (washingtonpost.com)
   • For big‑city systems serving about 15% of U.S. public school students, an Education Week tracker shows that as of May 24, 2021, most were finally open for wide‑scale or limited in‑person learning, implying that many students spent a large portion of 2020–21 either fully remote or in a relatively stable hybrid mode—not in constant open/close cycles. (edweek.org)
   • Some local leaders explicitly tried to avoid the stop‑start pattern Sacks described. For instance, Fresno Unified’s superintendent in early 2021 said the district would wait for better local conditions before reopening, specifically because “we can’t do this ‘start then stop, start and stop’,” and wanted students to stay in once they returned. (abc30.com)
   • That said, the CDC closure data do show that millions of students in certain states experienced one or more temporary COVID‑driven closures, and a minority of schools had multiple closures, so some communities did live through genuine stop‑start disruption. (wwwnc.cdc.gov)

Overall assessment

Sacks correctly anticipated that:

• Schools would invest in detailed mitigation plans with small cohorts and adjusted schedules.
• COVID cases in school communities would trigger some reactive closures and disruption.

However, the central mechanism and scale he predicted—schools widely reopening in fall 2020 and then quickly closing again at the first detected case, producing a generally stop‑start year for families—did not match the dominant U.S. pattern:

• Many large districts did not reopen in person at the start of the year at all, instead remaining remote for months. (edweek.org)
• Where schools did reopen, full‑school shutdowns were relatively rare compared to the number of schools and cases, and were usually tied to multiple cases or community surges rather than a single case. (cdc.gov)

Because the key claim—that reopening schools would typically slam shut again after a single case, making the 2020–21 school year broadly stop‑start—is largely inconsistent with the available data, the prediction is best classified as wrong overall, despite capturing a few elements (elaborate planning and some localized disruption).