The chair of the parents' association at Holland Park school has accused Colin Hall, the head, of being autocratic, and alleged that he ignored parents' views.
As The TES reported last week, the modernising Mr Hall faces a groundswell of discontent from parents and staff at the high-profile London comprehensive.
Members of the National Union of Teachers have voted overwhelmingly to pursue strike action over the withdrawal of time in the week for teachers'
representatives to pursue union duties.
Parents, who passed a vote of no confidence in Mr Hall in the summer, renewed their attack at a tense and inconclusive annual parents' meeting on Monday.
Now Neil Ferguson, chair of the Holland Park School and Community Association, has written to The TES denying that opposition to Mr Hall's changes, which include the introduction of setting and uniform, is Luddite.
"Parents, staff and pupils all have different views regarding uniform, setting, banding, intelligence testing and CCTV throughout the school," he wrote. "However, we are united in our dislike of the new regime."
Mr Ferguson claims the head "has ignored parents' views even when he has an obligation to take them into account" and says "numerous good teachers" have left the school since Mr Hall's arrival.
Asked about staff morale and resignations at Monday's parents' meeting, governors cited the high turnover in London schools.
But a resignation letter from a teacher at the school to the chair of governors, which has been passed to The TES, says she resigned because of the "disdainful" way staff were managed and says she had no other job to go to. She claims this is true of other members of her department who also resigned in the summer.
The letter criticises "the provocative classification of staff into those considered deserving of grace and favour and those at the other extreme who were demonised, creating a most unpleasant atmosphere of suspicion and mistrust".
Mr Hall declined to comment on Mr Ferguson's letter.