What is perennialism?

The main idea of Perennialism, in my opinion, is that only unchangeable truths or principles regardless of time and place are worth being included in the school curriculum, not even facts if they have tendency to change over time. It sounds to me that perennialists want people to learn from the past so that they can avoid their mistakes then step on the past to build their brand new future. Perennialism is a teacher-centered educational philosophy that focuses on everlasting ideas and universal truths. "Perennialism, which is derived primarily from the writing of Plato, view truth and nature - in particular, human nature - as constant, objective, and unchanging." (Ryan, 2018, p.283)