A mother is furious after she received a letter from her son’s school criticising his attendance, despite the fact he had been fighting a deadly illness. Vicky Tassari, from Gravesend, was shocked when she opened the correspondence from Northfleet Technology School in Colyer Road complaining her son’s attendance was “in a worrying state”. Vicky, 35, said: “I was disgusted to receive it. He has had a stem cell transplant and is lucky to be alive.” After contacting the school, Vicky was told it was an administrative error and the letter should never have been sent. But she was fuming when the he…