The Coseley School in Dudley has 557 pupils - just over half its 975 capacity - and last year's GCSE results placed it bottom in the borough.
About 100 people protested outside Dudley Council house on Monday as the decision was made to put the closure plan to the public.
The consultation will run until 5 April, with a decision due in May.
'Safe haven'
If the plan goes ahead, years seven, eight and nine will go to different schools next year.
Current year 10's would stay and complete their GCSE's with the school shutting altogether in August 2017.
Head girl Tatiana Davies protested with fellow pupils against the closure.
She said: "This place is like a safe haven for kids and it's a community that's being ripped apart by the council.
"It's not fair whatsoever that they've made a decision to do this... We care about our school so much."
Councillor Ian Cooper, cabinet member for children's services, said: "Proposing the closure of the school is very much the last resort and not something we have taken lightly.
"During recent years it has experienced a dramatic decline in pupil numbers, which are forecast to drop even more over the next three years, as well as results below the national minimum standards.
"We know the school has worked hard to try and raise attainment but unfortunately all these factors have led us to take this action."
Only 54 parents have chosen the school as their first preference for September 2016 and the council says the school is facing a Â£1m shortfall.
Ofsted rated the school "inadequate" following an inspection in September 2012 and "requires improvement" in September 2014.
A school with low pupil numbers and grades could close under plans being put to the public.