The state's provider of primary school ethics classes is making an aggressive push for parents to sign up for the scripture alternative ahead of the new school year.

Primary Ethics has almost 100 screens at train stations across Sydney advertising the classes, as well as a short television commercial.

Ethics, the ad says, "teaches kids how to think not what to think". Credit:Quentin Jones

The interactive signs pose the question: "Mum, why is it OK to kill cows and sheep but not to kill whales?"

Ethics, the ad says, "teaches kids how to think not what to think".