Is my child too ill for school guidance from the NHS:

https://www.nhs.uk/live-well/is-my-child-too-ill-for-school/

Children with minor illnesses like a common cold or mild cough can go to school, but should stay home if they have a high temperature (over 38°C), vomiting, or diarrhoea. You should keep them home until they have been fever-free for 24 hours and a temperature-free, and until there have been no episodes of vomiting or diarrhoea for at least 48 hours. For other infections, or if you are unsure, call the school on the first day of absence and consult a pharmacist, GP, or the NHS 111 service for advice. 

All school absence must be communicated to the school office in line with our attendance policy and procedures.