It is perhaps an understatement to say that activists in England’s teaching unions don’t always see eye to eye.

But any professional disunity in this country pales into insignificance compared to the bitter - and violent - row at a teaching union conference in Mexico last week.

A video shows the moment the meeting descended into chaos, as fighting broke out and chairs were thrown. According to the Mexican site Meganoticias, 15 teachers were injured in the brawl, some with head injuries and broken noses.

They include members of both the National Union of Education Workers (SNTE) and the National Education Workers Coordinator (CNTE). Ironically, the banner on the wall of their conference room reads ‘unidad’, meaning ‘unity’. 

There are conflicting accounts of how the fighting broke out, with some reports suggesting it was instigated by private security guards that were hired to protect teachers.  

Some teaching union members in Mexico have been involved in violent protests over the past few years, amid controversy over government reforms such as the introduction of new tests of teachers’ subject knowledge and pedagogical skills.

TES reported in January that a group of teachers had sabotaged test centres where these assessments had taken place.  A government source said activists were using “violent means” to prevent teachers from taking the tests.