Hasmonean High School has confirmed it will comply with an order to amend its admissions procedure.
The Orthodox state school said it was "reviewing and updating our admissions policies to ensure that we abide by the current regulations regarding admissions, that our school's ethos is upheld and that we reflect the needs of the Orthodox Jewish community."
The move comes after a complaint was upheld by Office of the Schools Adjudicator (OSA).
The Fair Admissions Campaign had objected to questions the school asks about prospective parents' levels of observance.
One of the questions asks whether parents observe "the laws of family purity". This alludes to a couple's abstention from sexual relations for seven days after a women's period, and her use of a mikveh to purify herself.
In his report, the OSA adjudicator said that it was not unreasonable to ask the question, but that it was impossible for a rabbi to "objectively assess whether or not a family observes the laws of family purity".
The adjudicator found that other criteria on assessing observance also did not meet the OSA's requirements to be clear, objective and fair.
The school, in Hendon, north-west London, has until February to make the amendments.
