Telling children that school is optional because it is hot outside is no small thing, and it’s not the only system breakdown that is making parents boil over with rage. Families have got to stop being an afterthought in this country, writes Mumsnet founder Justine Roberts Y esterday, a third of Mumsnet’s most active threads were about the heatwave . More than half a million words have been posted about it in the last few days alone. Not beaches, barbecues or paddling pools with mysterious