The warning is to be issued by the director of the sector who has simultaneously stood by a move to sack a kindergarten teacher for enrolling her own child into a state secular school.
Some 230,000 children attend state religious schools in Israel - around a quarter of all those enrolled in the state sector.
About 50,000 pupils in these schools are thought to come from homes where religious observance is lax.
Reports are circulating that some religious schools have linked the admission of pupils to declarations by their parents that religious rituals and practices are observed at home. Parents have reportedly been asked to confirm that they keep the Sabbath and observe dietary laws, and that the men in the family cover their heads all the time.
"We believe that this is not only illegal, but contrary to our values, " said Matityahu Dagan, director of the education ministry's state religious school division.
"We should accept all those who want to have a religious education, even if their parents are not religious. The only condition should be that pupils are ready to accept our curriculum, (in the school) which means religious studies, prayer, and modest dress and behaviour."
He invited any parent to complain directly to him if they felt that religious schools were not complying with admission rules.
In a separate development, it emerged last week that a teacher at a religious kindergarten in the northern town of Nahariyya was removed from her duties because she had signed her child up for a secular school.
In a letter to the chair of the Knesset (parliamentary) education committee, teacher Anat Tubul said she had been given two choices: to sign her child up for a religious school, or to start working as a supply teacher in the religious sector - a move she refused. Mr Dagan said Ms Tubul had now accepted the suggestion of transfer to a job in the secular sector, and attempts were being made to find her a position.
"Education is not a shoe shop," he said. "The shoe seller can sell things she doesn't like. In religious education, you have to believe what you are teaching."
He said all applicants for teaching jobs in state religious schools signed an agreement saying they identified with the goals of state religious education, and would send their own children to religious schools. "This teacher was breaking her agreement."
Amnon Rubinstein, Israel's education minister, is to look into the principle of the matter, said a spokesman, adding that his room for manoeuvre was limited.
Israeli law provided religious schools with significant autonomy, and any changes would have to come about through Knesset legislation.