Parents have written to the Welsh government calling for a delay to the introduction of the new Relationships and Sex Education (RSE) curriculum until after a judicial review is heard.
The controversial curriculum is due to start in schools across Wales from September.
It has drawn concern around the teaching of sexuality and gender identity.
Under the curriculum, sex education will be taught to children from the age of three, with no right for parents to withdraw their children from the lessons.
Public Child Protection Wales (PCPW) was granted a judicial review into the curriculum but the Welsh courts have delayed hearing the case until after the start of the new academic year.
The case is expected to be delayed beyond that as the Queen's Counsel appointed by the government is not available until November.
Over 5,000 people backed PCPW's petition for a judicial review, which was granted in May after the High Court declared that the Welsh government's plans involve "the consideration of complex constitutional matters with potentially very significant consequences for both parents and children".
PCPW has written to the Welsh government asking that it withhold implementation of the RSE curriculum until after the judicial review has been heard.
The campaign group is also asking that in the event that the Welsh government insists upon rolling out the curriculum, parents be given the right of withdrawing their children from the lessons until judgment has been made.
PCPW co-founder Kim Isherwood said: "We believe the Welsh government should respect any order of the High Court, and should not seek to prejudge the outcome of any decision.
"We have therefore written to the government to obey the 'spirit' of the judgment handed down by Mr Justice Turner until the Judicial Review decision is known."
She urged the government to appoint a different counsel so that the judicial review "can proceed without delay".
"This is the sort of bureaucracy which makes the electorate mad, and ministers should put it right immediately," she said.
"It is also clear that administrators in Cardiff have not taken on board the seriousness of the issues concerned, and should urgently seek dates from both parties for July or August – ahead of the start of term.
"This is about our children and their futures."
