This paper analyses the ethical principles involved in the prescribed high school textbooks to find out whether the text and supplementary books in the high school contain materials of ethical values which conform with the generally accepted principles of ethics. The study has taken into consideration English grammar books, Filipino language grammar books, and history books. In conclusion, the paper notes that the all the books have a certain percentage of ethical principles involved, and while that percentage is considered to be rather small, those books are still considered to be acceptable teaching materials.