Students from 14 schools and sixth-form colleges in London, Birmingham and Derbyshire have been working with the architects.
The schools will present their designs at five regional finals; the winners will go on to be showcased at a final at the RIBA in June.
The project has been organised by the RIBA, the Learning and Skills Development Agency and Arts Council England.
Paul Hyatt, president of the RIBA, said the scheme was a great opportunity for students to learn about design.
He said: "It demonstrates that everyone, young and old, has a vital role to play in the design of the urban environment in the UK."
Projects that have been "redesigned" include Arsenal's football stadium and the Stephen Lawrence Academy in London.
It will include a library, housing, car parking and possible retail space. It is hoped that the library will include an integral heritage centre.
West Sussex council said it intended to invite six architects to a competitive interview.