Indian Self-Determination and Education Assistance Act

After learning about the Indian Self-Determination and Education Assistance Act I am a little bit confused about how the reservation near where I live is run.  I live close to the Seneca Nation of Indians Reservation near Irving, NY which is about half an hour from Fredonia.  I understand that this act was set in place to have the Native Americans take control over their own government run institutions, but also had help and encouragement from the federal government in doing so. One of the things that confuses me most is the education system set in place on the reservation.  First off, do these schools have to follow the NYS curriculum like all other schools have to with the NYS testing and everything?  If not, then do the schools vary and get to choose their own system of teaching?  In my thinking, I feel as though it is that these schools don't have to follow NYS standards.  My basis for this is that the high school I went to is about 5 minutes from the reservation and we had many Native American students in our school.  We had such a large number of Native American students that there was a class made specifically for them, in which no one else was allow to take part in, where they could learn their native language as well as all about their culture.  I guess this just confuses me because if there are schools on the reservation, why aren't those who live on the reservation utilizing the schools that they build and are paying for?  I would completely understand if they would get a better education at a NYS school rather than a school that was on the reservation, so I guess my big question is: How are students on reservations taught? Is it by NYS standards or the reservations standards?