As most people know, religious education and prayer were taken out of the public school system after a Supreme Court ruling in the early 60's. However, teaching the Bible was not.
In a National Catholic Register article Janneke Pieters writes that, in recent years, studying the Bible is becoming more prevalent in American high schools. It's not only constitutional, it is being encouraged as a way of understanding the world we live in:
Many welcome the return of the Bible to public education. According to the Bible Literacy Project website, in a 2006 survey of English professors from Yale, Harvard, Princeton, Stanford, Texas A&M, University of California-Berkeley and others, all agreed with the statement: “Regardless of a person’s faith, an educated person needs to know the Bible.” Another 2005 study showed 98% of high-school English teachers agreed Bible literacy was academically advantageous.
“The conclusions of these studies were that students do need to know about the Bible in order to be conversant about Western literature and culture,” said Sarah Jenislawksi, executive director of the Bible Literacy Project. “So many works of literature were written assuming readers would understand these [biblical] references.”
The works of Shakespeare alone contain 1,300 biblical allusions. John Milton’s works draw heavily from the Bible. Much of Martin Luther King Jr.’s teachings and writings are incomprehensible without knowing the Bible, and the same could be said of many great American leaders. And the Advanced Placement English exam is rife with biblical allusions.