What are the official and unofficial reasons why Chuck was kicked out of school in Chapter 7 of Tisha?

The official
reason why Chuck is kicked out of school is that his enrollment is in violation of the law.  The
unofficial reason for his exclusion is a deeply ingrained attitude of racism and
hatred.

Chuck is the half-breed son of one of the inhabitants of the
settlement of Chicken, Alaska - Joe Temple.  The child has recently been brought from a
neighboring Indian village characterized by squalor and extreme poverty.  Although he can read
and cipher after a fashion, Chuck's ways are different, and he speaks only limited English.  The
denizens of the settlement call him a "siwash", a demeaning...