Children have been told to take 'zero days off' school – even if they're ill with tonsillitis or glandular fever.
The new guidelines - which parents have described as 'a joke' - have been given to families in South Wales and state that there are very few reasons for pupils to stay at home.
Kids are required to attend if they suffer from a range of childhood complaints such as conjunctivitis, head lice and threadworm.
And they should spend no more than four days away from school for measles and take no more than five days for chicken pox, whooping cough and mumps.
The guide, which was produced by a consortium of five local councils, including Cardiff, says families should seek advice from NHS Direct or consult their GP before making a decision to remove their child from the classroom.
The booklet states that a child with tonsillitis should not have any time off school, with parents simply told: "There are many causes but most are due to viruses."
For chickenpox, parents are told to keep children off schools for 'five days from onset of rash', adding: "Keep away from vulnerable children and pregnant females."
Children with mumps should be keep off for 'five days after onset of swelling', although parents are told it is 'preventable by vaccination'.
The councils involved insisted the advice was obtained directly from the Health Protection Agency and the Royal College of Paediatrics and Child Health.
Parents have criticised the advice as unworkable. Gareth Whittle, a father-of-two from Cardiff, said: "I thought it was a joke. I think as parents we are responsible enough to know when and for how long we should keep our children away from school."
Pauline Jarman, a governor at Caegarw primary and Mountain Ash comprehensive in Rhondda Cynon Taff, told Wales Online: "When I had glandular fever I was too run down to function.
"I am inclined to trust the judgement of the parent or guardian. If they think the child's illness is severe enough to keep them home – or are eager to avoid spreading the illness to other children – they will seek the appropriate advice from their GP."
A spokesperson for Rhondda Cynon Taf Council, one of the authorities involved, said consultation had been carried out with Public Health Wales and a series of university health boards 'who all approved the content of the advice table'.