Section 48. Any school or person offering courses in preparation for civil service examinations shall cause to be printed in bold type on all its advertisements and circulars and all contracts to be entered into with prospective students a statement that disabled veterans who qualify for appointment must be given preference for appointment over veterans and non-veterans and that veterans must be given preference over non-veterans. Whoever violates the provisions of this section shall be punished by a fine of not less than fifty nor more than five hundred dollars.