Teachers have walked out in the first of six planned strike days in a row over management at their school.
Members of the NASUWT at Ysgol Uwchradd Aberteifi, Cardigan, say they are working in a “climate of fear and intimidation”.
Five further days of strike action are planned for February 4, 5, 13, 14 and 15.
Ceredigion County Council said it has commissioned an independent investigation following issues raised by former staff members at the school and takes all such allegations seriously. The investigation is due to finish by the end of January.
Neil Butler, NASUWT National Official Wales, said union members at the school, past and present, contacted the NASUWT last October with information on what he described as unacceptable management practices, including “punitive and excessive monitoring and unreasonable workload".
“The NASUWT ballot for industrial action shows that the overwhelming majority of NASUWT members believe that there is a climate of fear and intimidation in the school and are willing to make a stand to secure change,” he said.
“The NASUWT is committed to protecting its members wherever they teach from unacceptable management practices and that is why we are taking action today.
“Whilst we deeply regret the disruption to pupils and parents, the action will continue until we are convinced that both the local authority and the governors are committed to changing the culture in the school.
“Teachers are professionals who should be enabled to work in a spirit of collegiality and cooperation, feeling they are valued and their professional opinions are respected.
“The NASUWT remains willing to engage with the employer to work towards this objective.”
A total of 16 NASUWT members are taking part in the walk-out at the school which has around 500 pupils aged 11 to 18.
The school, described as "naturally bilingual" by Estyn was under monitoring by the education watchdog until 2016.
Ceredigion Council said in a statement: "The school wishes to reassure parents and pupils that Ysgol Gyfun Aberteifi will remain open to all pupils, and provisions are in place to ensure that a full programme of meaningful learning will continue to be delivered on all of these dates.
"The action is taking place because of a dispute over alleged adverse management practices at the school. The NASUWT teachers’ union held a ballot because of this dispute, and 17 teachers at Cardigan School voted in favour of potential strike action.
"The Council has held a constructive meeting with the NASUWT and appreciate their role as advocates for teaching staff in Ceredigion schools. The Council wishes to continue to negotiate with the NASUWT and reach a resolution on the matters raised. The council has been and is, available to negotiate further with the NASUWT."
The independent investigation by the council has involved has spoken to 25 former and existing members of staff, including many who have not made any kind of complaint, the council said,
The investigation focuses on three main issues:
• Complaints against school leadership, including whether a culture of intimidation, bullying and harassment exists at the school.
• Considering whether a group of teachers and former school teachers have co-ordinated a plan to intimidate, bully and harass members of the senior leadership team.
• Establishing whether any of the actions investigated contravene the Code of Professional Conduct and Practice for Registrant with the Education Workforce Council.
"The Local Authority takes all allegations very seriously and wish to work with all involved to secure long term beneficial outcomes for all, " the council statament added.
"All enquiries are expected to be completed by the end of January, and the County Council will then act in accordance with the recommendations of the report."
Chris Keates, general secretary of the NASUWT, said the union was disappointed to be forced into taking strike action.
“The union has met with representatives from Ceredigion County Council and the discussions were constructive,” she said.
“However, there is still no tangible evidence that there is the will to make significant changes at the school following amendments to the employer’s own investigations which seem to focus on threatening those who have had the courage to raise their concerns with breach of the Education Workforce Council code of conduct.
“The NASUWT stands ready to work with Ceredigion County Council and governors at Ysgol Uwchradd Aberteifi to create a working environment based on mutual professional trust and respect where staff are treated with dignity.”
The action follows a series of strikes by NASUWT members in schools in Wales last year over redundancies.
Members of the NASUWT went on strike over job losses at Chepstow Comprehensive, Tonyrefail School and the now closed Tasker Milward and Sir Thoas Picton schools in Haverfordwest last year.
Sir Thomas Picton and Tasker Milward Schools amalgamated to become Haverfordwest High VC School in September 2018.
Ceredigion Council was approached for comment.
