Consultations have started on plans by St Michael's Catholic School, High Wycombe to create a satellite school on the site of the former Quarrendon School site in Aylesbury.
That means another branch of the school would run in Aylesbury with the shared management and resources.
The proposal has been put forward by the governors of the school, Buckinghamshire County Council and the Diocese of Northampton.
The school would cater for students between the ages of 11 and 19 and would originally have a year seven intake of 120 and would grow to have six forms of entry.
Consultations with parents and the local community will run until April 28, and two public presentations will be held: at St Edward's Catholic Junior School, Aylesbury, on Monday February 27, and at St Michael's Catholic School, High Wycombe, on Tuesday February 28. Both presentations run from 6.30pm to 7.30pm.
With 45,000 new homes planned in Buckinghamshire over the next 20 years, the county council is keen to act proactively to proved adequate schooling for the growing population.
Letters have been sent to all Aylesbury school Heads as well as neighbouring residents.
If the plan is approved, Headteacher Garret Fay and St Michael's governors would have overall responsibility for the satellite site and local governors would be sought to support the multi-site school's governance.
Zahir Mohammed, Cabinet Member for Education and Skills, said: "This is an important consultation and I hope people will take the time to respond, as their views are of great significance".