Powys County Council is looking for contractors to build the 150-place Ysgol Gymraeg y Trallwng in Welshpool, established in 2017 following a re-organisation process.
This will be a flagship project for the council, with it being the first 21st Century school built in Powys that will see the integration of old and new, the historical and the modern, councillors said.
The project will help the council deliver its Strategy for Transforming Education in Powys, an ambitious 10-year strategy that was approved earlier this year.
The new school will be built on the former site of Ysgol Maesydre with the old Grade II listed building, currently occupied by Welshpool Church in Wales Primary School, refurbished to accommodate early years and community facilities.
A new extension will be built to include a new school hall and classrooms.
The project was delayed after Dawnus Construction Ltd, which was awarded the contract, went into administration in March 2019.
Councillor Phyl Davies, cabinet member for education and property, said: “The publication of the tender package is a major step forward for this school building project after a disappointing delay after the previous contractor going into administration.”