Sorting out the testing is the key, not short, sharp lockdowns.
As another poster said, Covid has a long incubation period and it would have to be at least six weeks or nothing. Remember late March/April after lockdown, it took a good three weeks to start to see the numbers fall because of the incubation period.
Testing and tracing and sorting that fiasco out is the key here. A teacher I work with has taken a week off school, and it took 3 days to book a test (the testing centre refused to test because the code given was wrong - this happened multiple times in our area, and made local news) and when he finally got a test, it was over 72 hours to get the result.
The government are now going to fine people £10k for failing to self isolate after being contacted by Track and Trace because many people are ignoring advice to self isolate. But with such a delay getting results (after a long time trying to book a test) the emphasis must be on sorting out the testing, not fines.
We have only been back at school two weeks and four teachers have been off for far longer than they needed to be because of the slow testing system.
If the virus continues to grow as it is, we won't have enough teachers in school to keep open. That could happen within a month.