They claim the loss of key teachers and a policy of combining departments will damage the prospects of students. They also say the college, which wants to get rid of 40 jobs, has been secretive about its problems, created in part by a pound;15 million building programme.
The Rev Richard Franklin, who has a daughter at the college and chaired a recent meeting of around 70 concerned parents, said: "Transparency is paramount. I am not conversant with the full facts and feel I should be. The college seems to err on the side of telling people nothing."
Weymouth is the area's principal sixth-form centre. Some parents are worried about the prospects for A-level students in subjects such as performing arts and French. Christine Taylor, who organised the meeting, said: "We know there have to be cuts but the problem is secrecy. Rumours are circulating because no one is being told the truth."
The college, which hopes to achieve job losses through voluntary redundancies and natural wastage, says seven staff have gone and "several others are considering their futures". But some who remain say morale is low and complain of "macho management".
One said: "Senior staff have been undermined, ignored and unsupported. There has been unnecessary haste over departure dates and no consideration of the impact that will have on students." The controversial new building, for which the college borrowed pound;3.9m, is due to be opened formally on December 6 by the Earl and the Countess of Wessex. The college says it owes the LSC around pound;2.5m, having failed to reach income projections over several years.
The principal, Sue Moore, has written to students and parents about the situation and its likely impact. She says she has adopted "an open policy to speaking with students and their parents or guardians throughout".
Deputy principal Paul Lonsdale said in a statement to FE Focus: "For the majority of students nothing will change. Teaching will continue at the same high standards as in previous years. For a small number of students it will be necessary to change one or more of their lecturers. Where we do need to replace a member of staff, we will ensure well-qualified and experienced teachers are selected.
"It is always difficult to give full information without breaching an individual's right to confidentiality," said Mr Lonsdale. "Staff have remained fully consulted throughout by weekly meetings with Natfhe and regular meetings with Unison.
"Given the legacy of inaction by previous management the challenges have been considerable. The governing body, the Learning and Skills Council, our partner schools and many within our community fully support what we are trying to achieve."