Great questions. The kids mostly speak English as first language, and the schools are in English. With the exception of one huge twist, the schools have many educational difficulties you'll find in rural America generally—it's hard to get money for materials and curriculum, hard to recruit good teachers, hard to get students connected to people with practical advice/guidance, hard to get connected to opportunities, hard to reach escape velocity, and so on.
So, what's the twist? Tribal schools tend to be administrated by the federal government which makes problems extremely slow and hard to address. With some asterisks, the local elementary school was basically provisioned as a consequence of a federal treaty with the US Senate, and is/was mostly administered by a the Bureau of Indian Affairs (BIA), which rolls up into a federal department that until 2020ish, had never been run by a native person. All of these things make it very tricky to work with.
In spite of that, believe it or not, this is a massive improvement: until relatively recently, the school was a mandatory boarding trade school meant to teach kids to be (basically) English-only maids. This lead to a substantial percentage of the population being either illiterate or semi-literate, with no meaningful work experience, and with very very few opportunities that were not menial work. That inertia is extremely challenging to overcome, and the most natural place to try is the education system, which generally is simply not up to it.
I am stating these as a neutral facts on purpose. Regardless of how we got here, the hand is ours to play. Some of us got out and whether we succeed in the next generation depends on whether we can mobilize the community to productively take advantage of the resources we do have. This is why it's painful to me to hear about, e.g., land acknowledgements. If you have seen this pain firsthand I just do not see how that can be the #1 policy objective.