Commercial Alert and Obligation Inc. sent letters today to state officials in all 50 states requesting an investigation of an offer by Channel One, an in-school marketing company, to pay $500 to public school employees in exchange for convincing a school principal to enter into a contract to receive Channel One's product. The groups, which oppose the commercialization of schools, sent the letters to state attorneys general and chief state school officers in all 50 states, as well as to the heads of state ethics agencies.