The latest guidance for schools regarding Covid can be found by following the link below - this has remained the same since March 2022 when all restrictions were fully lifted.
In summary, testing is no longer mandatory, however if adults do test positive the advice is to try and stay at home, avoiding contact with people for 5 days. This applies to school staff.
The advice for children is to try to stay at home, avoiding contact with people for 3 days.