"No person in the United States shall, on the ground of race, color, or national origin, be excluded from participation in, be denied the benefits of, or be subjected to discrimination under any program or activity receiving federal financial assistance."
Key words: receiving federal financial assistance. It's a private religious school, meaning it is barred from receiving government funding.
If you meant Title VII, that is generally prohibited, but not in the case of religious organizations. Case law has found that they are free to discriminate in their hiring practices (https://constitution.findlaw.com/amendment1/annotation08.htm...). It also doesn't stop a non-religious company from doing so but not disclosing their reason to the terminated employee, which they have no obligation to do in right-to-work jurisdictions.
Furthermore, reservations sit in a gray legal zone where they are considered semi-autonomous sovereign nations. In practice this exempts them from state law, but they are generally subject to federal law.
"The EEOC does not have jurisdiction over charges of employment discrimination against federally recognized Tribes if the alleged discrimination is based on race, national origin, sex, color, or religion (under Title VII), disability (under the ADA), or genetic information (under GINA)."
Story has two sides to it. On one, you have a faith-based private school built on a native reservation with the explicit purpose of being as bigoted as possible toward the people living there, which is horrible, but on par for the behavior of such organizations. On the other, you have natives who continue to send their children to that school despite generations of this pattern because of better educational outcomes than the U.S. federal public school.
There are a few possible calls to action here. You're not going to convince the ministry to change their outlook -- you might as well ask an alligator to stop eating meat. As a religious organization they are exempt from many laws that would get government or corporate groups in trouble, particularly if the families signed a paper to enroll their kids. It comes down to biting the bullet and playing along with the school's BS, or biting the other bullet and seeking alternative educational providers. It would be great if as a community they could find their own path to creating better public schools (having the freedom to build casinos provides a readily-available revenue stream, if you can solve the leadership corruption issue), but failing that, I guess the U.S. federal government could throw more money at the Bureau of Indian Affairs.
I can emphasize with the kids because I grew up atheist in an overwhelmingly Mormon backwoods town, where I was the "devil worshiper" and treated like garbage for it. On the other hand, the families have alternatives available to them. If the alternatives suck, they should look into how to make them better.
The grills used by McDonalds are a bit more complex than a flat hot surface. They cook both sides of the burger simultaneously using "clamshells" lined with a heat reflective material, which automatically raise using hydraulics on a timer. Perhaps not as complex as an ice cream machine, but definitely not your griddle at home.
Edit: likewise, the fry machine has a self-propelled hopper which splits the raw fries up into batches.