Councillors have criticised proposals which could see Powys end up with just two sixth forms.
A Powys County Council learning and skills scrutiny committee meeting on Friday saw three options revealed as the outcome of a strategic review into post-16 education.
The preferred option would see a sixth form college with one management team set up across two sites in Brecon and Newtown, while another college would be set up across a number of Welsh medium schools.
Councillor Chloe Masefield, who represents Crickhowell, said she had "significant concerns" about the review.
The options will be subject to an "engagement" process which will allow people to give their views on the proposals over the next six months.
Council education staff stressed the current model with all schools having their own sixth form was not "financially viable".
The need to address post-16 provision has also been highlighted by education watchdog Estyn in a scathing report on the department published in March.
One option could see a sixth form college set up with one board of governors and management team across two sites in Brecon and Newtown.
Similarly, a sixth form college would be based across Welsh medium all-through schools at Ysgol Bro Hyddgen in Machynlleth, Bro Caereinion in Llanfair Caereinion and potentially Builth Wells.
The Welsh medium sixth form would be run separately.
