Her advice sounded like a Sunday-school lesson—too simplistic and moralizing.

Sunday-school 是由 Sunday（星期日）和 school（学校）组成的复合词。Sunday school 指基督教教会为儿童或成人提供的宗教教育课程，通常在星期日举行。 Sunday-school lesson 特指主日学校中教授的课程内容，常带有简单直接的道德说教特点。