In other words, the agreement would make it in the material interest of the public schools to get children to drink more Coca-Cola. Those inducements would compromise the integrity of the public schools. It is inappropriate for public schools to profit from the sales of Coca-Cola. The proposed agreement would allow Coca-Cola to advertise on vending machines and other product dispensers in the public schools. Advertising does not belong in a public school.
Advertising is a form of propaganda.
It often uses sophisticated psychological manipulation to subvert reason and promote sales. Advertising is antithetical to reasoning, and to teaching children how to reason. Allowing advertising in schools compromises the civic mission of schools and education. Seattle's children might understand this implicit endorsement to mean that it is good or healthy to drink Coke. That is the wrong message to send to Seattle's children.