The Lion Acadamy Trust wrote to parents stating its belief that the health of young children could be affected if they were not given sustenance and water, The Telegraph reported.
The decision has been criticised by the Muslim organistion in Britain and they said it was not the school's issue to interfere.
"There were enough rules in Islam to protect vulnerable from fasting," Muslim Association of Britain (MAB).
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We believe that there are sufficient and stringent rules within Islam which allow those who are unable to fast, to break fast," said a MAB spokesman.
"These rules include those who are medically ill or compromised; or too young or too old to fast.
"MAB ascertains that the final choice of whether or not to fast should be the right of the parents, who should in turn encourage their children to fast without forcing them to do so."
Dr Omer El-Hamdoon, the President of MAB added parents ought to have the ultimate say in whether their child participates in the fast.
"Schools should play a supporting role to parents; and issues like this should be discussed, not blanket enforced," he said.
Barclay Primary School, Sybourn Primary School and Thomas Gamuel Primary School in Waltham Forest and Brook House Primary School in Haringey belong to Lion Acadamy Trust.
However, in a statement published online, Justin James, CEO of the trust, said those parents who wanted their children to fast should contact the school and make specific arrangements.