De la Salle College in Salford became only the second out of 300 inspected to receive a grade five for management in a damning Further Education Funding Council report.
Principal John McDermott, in charge since 1990, says he is taking voluntary redundancy for personal reasons. Vice-principal Alan Bowden will leave when his one-year contract expires in a fortnight.
The inspection report says the college, which has many students from deprived areas, needs to address its weaknesses urgently. Problems include weak management, vague and out-of-date strategic plans and a lack of involvement by governors in checking progress.
The college is now preparing an action plan for next term. Managers deny merger or closure are being considered.