The state school in Melilla, one of Spain's two north African enclaves, is almost exclusively attended by Muslim pupils.
But as Ramadan got underway last week, the headteacher of Juan Caro primary school sent home an advisory letter.
"Observing Ramadan could provoke episodes of lightheadedness, migraines and sunstroke as a result of dehydration or lack of sustenance," warned the letter penned by Alfonso García Zafra.
His letter was accompanied by a missive from the Islamic studies teacher which pointed out that “students who have not reached puberty – and all who study here are under 12 – are exempt from fasting under Islamic teaching".
"So I advise - and am supported by the Islam teacher - that parents follow this recommendation because of the host of activities planned until the end of term, and because of the heat."
During Ramadan, Muslims are expected to fast – refraining from eating or drinking - between dawn and dusk.
But some parents were said to be furious at the dictate.
Dris Mohamed Amar, the leader of Melilla's Islamic Council, said a school had "no place interfering on religious matters," according to local paper El Faro Digital.
He also said that the school could not dictate when a child reached puberty, the age from which Muslims are expected to observe Ramadan.
"It is up to parents and not the school to decide whether they have reached puberty and whether or not they should observe the fast," Amar told El Faro.
José Manuel Calzado from Melilla's department of education sought to soothe tensions by insisting the letter was only intended to "remind parents that the school year was not yet over and that physical activities may form part of the curriculum and that fasting was not compulsory for children."
More than 50 percent of the population of Melilla, a city enclave of 12 square kilometres that borders Morocco, are Muslims.