Teachers at a Wearside primary are continuing with strike action in protest over academy conversion plans.
The members of the NASUWT at Highfield Community Primary School have spent their third day on the picket line following proposals to merge with another school in the city.
They are concerned about their future health and wellbeing if the governing body goes ahead with plans to form an academy partnership with Valley Road Primary School.
John Hall, national executive of the NASUWT, said the teachers started to raise concerns after Valley Road Primary School first became involved with Highfield in Autumn last year.
He said more than 100 grievances, all involving alleged breaches of Sunderland City Council's bullying and harassment policy, from his members at the Ford Estate school are currently under investigation.
Mr Hall said: "We are not talking about one or two incidents, we are talking about more than 100. Our members are not prepared to work for an employer where they do not agree with management practices."
He said they have been given a lot of support from other staff members at Highfield, who are in different unions and parents have also been very supportive.
A meeting with governors and Sunderland council bosses has been scheduled to take place next week.
Mr Hall said he wanted to stress that members are not against becoming an academy, just not with Valley Road.
He said members believe there is the potential to result in adverse management and working practices, job security and changes to pay and conditions of service if the move goes ahead.
Mr Hall said: “The teachers are concerned for their future health and wellbeing if the governing body goes ahead with its support of forming a partnership between Highfield Community Primary School and Valley Road Community Primary School as part of the Iris Trust.”
If the issue is not resolved the NASUWT members at Highfield have further strike action planned for May 16, 17 and 18.
A spokesperson from Sunderland City Council said: "The governing body of Highfield Community Primary School has agreed to meet with representatives from NASUWT on Tuesday, May 9, with the aim of quickly reaching an agreement to resolve the situation.
"The governors are keen to ensure through these discussions that any decisions taken on the future of the school are made with the best interests of current and future pupils at heart.
"Highfield has continued to remain open throughout the strikes, with the majority of staff attending work as normal."