A teacher's insults towards pupils over fake tans and their weight in the run up to the school prom were "reasonable comment", a hearing was told.
Alexander Price, who also mocked colleagues and parents, commented in a blog under the name Provoked Pedagogue.
Some comments were made after Denbigh High School was put in special measures in 2018 by the inspectorate Estyn.
An Education Workforce Council committee was told Mr Price's views reflected what inspectors found.
The school was reprimanded after failing to improve following a critical report.
Comments appeared on the blog between 2016 and 18, but Mr Price initially denied he had made them.
'Pull wool over eyes of inspectors'
The school was not named, but some teachers said Denbigh High was clearly referred to, the fitness to practise committee heard.
In one post, the school's senior leadership team were described as "trying to pull the wool over the eyes of inspectors".
In another management's overall performance was criticised.
Former design and technology teacher Mr Price later admitted he had published the posts, the hearing was told.
In another one, under the title "The Problem with Prom", he mocked pupils and their parents for making so much effort for the school prom by spending sums they could not afford on gowns and make-up.
Referring to poorly applied fake tans, he wrote "the literacy was so poor they can't read the instructions."
Mr Price referred to "overweight girls being shoehorned into gowns and paraded through the town like cattle."
He said the "proms mean more to them than GCSEs."
Dr Paul Evans, who became head teacher in 2018 having worked at the school since 2012, told the hearing he was easily identifiable in an item on Mr Price's Twitter account.
Sacking appeal rejected
He said he found the comments hurtful as they questioned his professionalism, and he also feared it would affect efforts to get the school out of special measures.
Mr Price, who was sacked and had his appeal against the decision rejected, faces four allegations of unacceptable professional conduct by making offensive or derogatory comments.
NASUWT union official Colin Adkins, told the committee the comments could not be classed as derogatory or offensive as they were "reasonable comment or reasonable professional opinion".
"An attack on Mr Price is an attempt to provide a cover-up of the school's failings," he said.
The hearing continues.