The DfE has published further guidance ahead of Step 4, as follows:


Daily contact testing trial
The University of Oxford has published a report outlining the initial findings of its study into daily contact testing (DCT) in secondary schools and colleges. The aim of the trial was to weigh up the benefits of DCT to keep pupils and students in face-to-face education while reducing the risk of transmission. The initial findings suggest that the schools which undertook DCT instead of isolation, did not see a greater increase in transmission.
The government has said that it will “consider the findings of the trial, including any potential implications for government policy, before any decisions are made on how DCT may be used in schools and colleges”. The current plan for the autumn term is that children and fully vaccinated adults won’t be required to either self-isolate or undertake DCT after 16 August, but instead will simply be advised to take a PCR test.