The standardisation of the school year, promised by the Minister for Education and Science, could be unconstitutional unless it marks all religious holidays of different denominations, according to Educate Together chief executive, Mr Paul Rowe.
Pupils of various religious backgrounds, such as Muslim and Jewish religions, should not have their holidays determined by the Catholic calendar, he said.
"It would be unconstitutional to insist, for example, that the Jewish school hold classes on Yom Kippur," he stated.
Under Article 42 of the Constitution, Irish citizens should not be compelled to send their children to schools with ethos contrary to their conscience or preference. "There is a huge human rights liability for the Department of Education to consider," Mr Rowe said.
The popularity of Educate Together schools amongst parents has made it the fastest-growing education movement in the Republic.
It was announced at the Educate Together annual general meeting in Galway on Saturday that the Department of Education and Science has approved a further six Educate Together schools for the 2003-2004 school year. One of the new Educate Together schools, in Lucan, has a "state-of-the-art" unit for 11 students with autism. It includes a sensory garden and occupational therapy rooms.
Educate Together, a non-denominational, community-based education movement, has been so successful that it has an application with the Department of Education for its first secondary school.
There are currently 28 Educate Together primary schools with 4,229 pupils.
Parents are attempting to enrol their children in Educate Together schools, despite the primitive conditions of many Educate Together school buildings.
One school is held in an Order of Malta hall, another in a converted stables. A school of 32 children in Donabate, Co Dublin, has been established in a Sea Scout cabin divided by a curtain.
Teachers have to pack up books and other equipment every evening, then reorganise their rooms the following day.
"There is no doubt of this school's viability and the State has reserved a site," said Mr Rowe.
The Donabate school's predicament is typical of Educate Together schools. The Griffeen Valley Educate Together school is located in a scout den in Lucan, Dublin, which has a maximum capacity of 24 students, although 153 junior infants have applied for places in September 2003, far above capacity.
This oversubscription of places is typical of Educate Together Schools, according to Mr Rowe.
"While 99 per cent of primary schools are of Catholic ethos, many parents want an ethos that recognises the growing diversity of Irish society," he stated.