Teachers at Holton Primary School in Barry are striking after they say concerns raised over their management have not been addressed.
Members of the NASUWT, The Teachers' Union, say "inappropriate" treatment and staff restructuring has had an impact on their health and welfare.
The strike is planned to continue for six days.
The union is urging the employer to "take its duty of care to its employees seriously."
The local authority is being urged to address the issues.
A spokesperson for the Vale of Glamorgan council said: “We are disappointed that the NASUWT has decided to take this course of action when lines of communication remain open.
"As an Authority, we remain committed to further engagement with the union in an effort to get this matter resolved at the earliest opportunity.”