Ysgol Gyfun Gwynllyw to add nursery and primary classes
Plans to extend the age range at a Welsh medium high school in Torfaen have been approved by council leaders.
Ysgol Gyfun Gwynllyw, in Trevethin, Pontypool, will start taking pupils from the age of three in 2021.
The school was recently placed in special measures after inspectors from Estyn found a range of shortcomings.
Senior council officer John Tushingham said the £6m project offered benefits such as a smooth transition from primary to secondary school.
The meeting of Torfaen's ruling Labour cabinet heard there was a growing demand for Welsh medium education in the county borough.
"Clearly we have got aspirations for it to grow and those aspirations are supported by the Welsh Government," said Mr Tushingham, head of access and engagement for Torfaen.
It will be the first school in Torfaen to cater for children from the age of three to 18.
Plans include an on-site nursery for 30 full-time equivalent three and four-year-olds.
Welsh medium primary school catchment areas will need to be changed as part of the plans.
However, council leader Anthony Hunt said the proposal would not have any impact on English medium schools being developed in the borough.
Ysgol Gyfun Gwynllyw will continue to accept secondary school pupils from neighbouring authorities across the wider Gwent area.
During consultation there was a single objector who raised concerns over traffic, a lack of safe pedestrian routes and worries about the age gap between some pupils, according to the Local Democracy Reporting Service.
Councillors were told traffic issues would be considered in more detail when a planning application was submitted for the scheme.
One idea also being explored is having different start times according to age groups, the meeting heard.
Last week, the education watchdog Estyn called for an action plan from the school, which it said urgently needed to improve standards, leadership, and the quality of teaching.