The department’s guidance on implementing protective measures explains who should and should not attend nurseries and schools, and sets out the measures that should be followed for staff that are either clinically vulnerable or clinically extremely vulnerable, or who live with someone in either of these groups. This guidance can be accessed here: https://www.gov.uk/government/publications/coronavirus-covid-19-implementing-protective-measures-in-education-and-childcare-settings/coronavirus-covid-19-implementing-protective-measures-in-education-and-childcare-settings.
Whilst other staff should be able to come into school, it is natural that some staff will be worried about doing so even if the risks for them are very low. In agreeing the best approach for their schools, headteachers and school leaders should work closely with employees and unions, where appropriate. School leaders will be in the best position, knowing their staff and school circumstances, to decide how to proceed in individual cases.