Section 55. A child infected, or in a household where a person is infected, with a disease dangerous to the public health as defined in accordance with section six of chapter one hundred and eleven, or in a household exposed to contagion from any such disease in another household, shall not attend any public school while he is so infected or remains in a household where such infection or exposure exists if the regulations of the board of health require such exclusion. A child returning to school after having been absent on account of such infection or exposure shall present a certificate from the board of health or its duly appointed agent that the danger of conveying such disease by such child has passed; provided, that if such a child returns to school without such a certificate, after having been absent on account of such infection or exposure, he shall immediately be referred to a school physician for examination and, if it is found by such physician upon such examination that such danger has passed, he may remain at school.