Secondary schools are failing to hold daily acts of collective worship and so limiting pupils' "spiritual and moral" development, Church leaders warn.
The legal duty of daily worship is not widely observed in schools
Senior leaders from the Christian churches said teaching staff needed more training in how to run religious assemblies at England's schools.
They signed a letter to Education Secretary Alan Johnson, calling on him to enforce the daily requirement.
By law, schools must hold daily acts of worship - broadly Christian-based.
Parents can opt to remove their children from such assemblies if they wish.
The churches said most primay schools complied with the law but three out of four secondary schools did not.
In a joint statement accompanying the letter to Mr Johnson, the churches said collective worship "helps to equip young people to understand more about themselves, foster a sense of the aesthetic and to cope with life-changing moments."
They argue that failing to provide collective worship diminishes children's education.
Head teachers and others who lead assemblies need better training and resources, they said, adding that training for teachers and head teachersdid not cover daily acts of worship.
Chair of the Churches' Joint Education Policy Committee and Bishop of Portsmouth, the Right Reverend Dr Kenneth Stevenson, added: "This policy is not about criticising schools for failing to deliver what can, admittedly, be a tough demand.
"Schools need adequate support from a range of bodies, including faith communities, to help them meet the requirements and to provide collective worship worth celebrating."
'Contradiction in terms'
Head teachers' leaders said the churches had "missed the point".
General secretary of the Association of School and College Leaders, John Dunford, said: "The law compelling schools to conduct collective worship is a contradiction in terms - worship cannot be compelled.
"Even without the law schools would still have an obligation to develop the spiritual and moral education of children."
The Department for Education said collective acts of worship were already a statutory part of the school curriculum.
A spokesman said: "We agree that collective acts of worship are important to help promote tolerance and understanding among children and young people."
He added: "It is the responsibility of the head teacher, governors and local authorities to make sure these are carried out.
"Ofsted continue to monitor this as part of their inspection regime."
The British Humanist Association said such daily acts of worship were unlikely to be inclusive.
A spokesman said: "A whole school can do many things together but, lacking a shared religion, it is incoherent to believe that they can 'worship' together."
The association wants schools to hold assemblies which draw on a variety of faiths and traditions but do not involve compulsory worship.
The spokesman added: "Many schools do hold such assemblies, and it is a pity that practice which is workable, honest, and educationally and socially valuable, remains illegal and is sometimes subject to criticism from Ofsted.
"If any government energy is to be expended in this area it should be to reform the law to make inclusive assemblies compulsory, not to reinforce compulsory worship."