Once again, SCOTUS is going to have to suck it up and deal with drawing a legal line that is going to be almost impossible to articulate. Abington School District v. Schempp, 374 U.S. 203 (1963), opened this can of worms wide, thanks to a majority opinion that refused to clearly distinguish between mandatory teaching of the Bible as a cultural and historical cornerstone of Western thought, and teaching it as religious indoctrination. The dissent by Potter Stewart also still resonates, particularly this section:
“If religious exercises are held to be an impermissible activity in schools, religion is placed in an artificial and state-created disadvantage…. And a refusal to permit religious exercises thus is seen, not as the realization of state neutrality, but rather as the establishment of a religion of secularism, or at least, as governmental support of the beliefs of those who think that religious exercises should be conducted only in private.”
The facts are, and they are facts, that 1) The history of religion is inextricable from human history, 2) It is impossible to explain that without teaching what the relevant religions are, and 3) If a religion is explained and studied sufficiently to allow a rudimentary understanding of its significance, then that religion is being taught. I would add to those these facts: 1) Most teachers are incapable of handling the topic with sufficient nuance and competence to thread that metaphorical needle, and 2) The human tendency to bias makes trusting any teachers to even attempt this feat irresponsible.
The dilemma seemed more bearable back when an estimated 61% of American children attended Sunday School—my generation. Now the percentage is about 15%. The Catch 22: American have to understand religion to understand their own nation, its history, its culture and society, but public schools can’t be trusted to teach it, organized religions can’t be trusted period [See: Catholic Church child predator scandal] and parents are as untrustworthy as teachers, if not more.
My guess, and it’s just a guess, is that the Roberts Court will decline another temptation to overturn long-standing precedent, and hold that this law is indeed unconstitutional.
Ethics Alarms 
You earn the right to have autonomy through demonstrating produce. The modern education system fails to do so. Imagining what some of these teachers would assign for reading would basically make a further mockery of the education system.
Reading, riting, and rithemetic are the builing blocks of education, religion can be added to that withou ahrnot the individual. It was done when the NYC educational system was functional. We had what was then called release time. Each Wednesday we, the public school studnets were released to aattend relgious formation, The cahtolics went to st. ann’s, the jewish student went to beth shalom, the presbyterians went to the first presbyterian church. We had quakers who went to heir meeting house. Not many baptist or evangelicals inthe neighborhood at that time.
Thusday morning we all returned to Public school 120. No one attacked the other but each were grounded in the faith of thier choice. so when we recited the pledge of allegiance saying “one nation under God” we had a basis to underrstand.
Like it not, Christianity (and the ethical systems it wrought out over 1500 years) is inextricably tied to Western Civilization and the subset of Western Civilization that is the American Experiment.
There’s no understanding of how we got here or why we think our civilizational model is better without understanding some core principles that derive from “Athens”, from “Rome” and, gasp, from “Jerusalem”.
The Bible then, has useful and essential passages to read as part of the literary tradition called the “great conversation” that charts the internal dialogue of western civilization to the present day. It is therefore tied to our civilization and our educational goals of making good citizens in ways that the Koran, the Vedas, the Upanishads, the Bhagavad Gita, the Tripitaka, the Analects, the Guru Granth Sahib, the Tao Te Ching, the Avesta, et al, are not.