Oldbury Wells School, in Bridgnorth, says it told parents of its decisions on some courses this week and will be offering further support and guidance to any individual students affected by the decisions.
Lee Tristham, the school's headteacher, said: "Having completed interviews for potential candidates for September 2023, while at the same time responding to the financial challenge faced by all organisations across the education sector, the school had looked carefully at what their final course offer would be based on preferences given and what could be offered.
"It is common practice for post 16 providers go through a process where decisions are made regarding final provision, although normally this would take place following GCSE results being published in the summer and students accepting offers."
Mr Tristham said it had become apparent that certain courses would not run and has made the decision to "communicate this early to allow appropriate support to be given to any students who may no longer have a full match of subject choices.
"The school had communicated this to parents this week and will be offering further support and guidance to any individual students who will have been affected by the decisions taken."
Mr Tristham said communicating with parents is a key priority for the school, and "something our school has often been praised for."
He added: "We are always keen to listen and respond to any feedback from those across our school community and would encourage any families who have specific questions to contact the school to allow appropriate advice to be given."
A parent who contacted the Shropshire Star and who did not wish to be named was furious.
The parent said: "Students at Oldbury Wells School who had been hoping to continue their studies at the school's sixth form, have been left scrabbling for the exit door as the sixth form curriculum offering for 2023/24 was slashed.
"Students who had been promised favourable consideration in respect of course availability in exchange for not cultivating applications to study at other institutions, feel like they've been 'stabbed in the back' by the school's hierarchy, as they find themselves having now to apply elsewhere, after many other providers have closed their doors to new applications."
The parent said students were notified by letter at the end of the school day on the March 28 of the "swingeing cuts to courses" for next year.
The parent added: "Parents and pupils now fear for the future of sixth form provision in the town, as an exodus of prospective students gathers pace, bringing the viability of even confirmed courses into question.
"This whole process has been handled appallingly by school leaders, with pupils, parents and seemingly even teachers being kept in the dark.
"Parents accept that schools are operating in a challenging financial environment, as are we all, but proper communication and consideration for the school community costs nothing, and has been woefully absent in this instance."
John Boken, a spokesman for the National Education Union in Shropshire, said he was "at present" unaware of other providers and unsure of any other sixth form due to make changes to their curriculum.
He added: "The NEU are aware of the pressures on all phases of education at present, which has led to industrial action, with sixth form and colleges balloting currently in relation to the constant cuts the government have made to education."