Parents have been banned from attending future sports days by a primary school in Wales after claims of obscene language and threatening behaviour. Sheena Duggan, the headteacher at Pentrebane school in Cardiff, said staff had been sworn at in front of children. In a letter to parents seen by the BBC, Duggan said the behaviour had “worsened” over the past few years. She wrote: “As you know the safety, happiness and wellbeing of our pupils, your children, is paramount and…