A teacher stabbed last Wednesday at school in Trescore Balneario by one of her 13-year-old students was released Monday afternoon from hospital.     The 57-year-old teacher from Berzo San Fermo, Chiara Mocchi, was hospitalized at Papa Giovanni XXIII Hospital in Bergamo.     It emerged Monday that the knife wielded by the student had come within a millimetre of Mocchi's aorta, and that another student had stopped the attack, kicking and punching the assaillant.     School officials said he