Is a company or school's violation of its own internal rules inherently negligence as a matter of New York law?

No. New York's courts have long held that the failure of a company or school to abide by its own internal rules will not, in and of itself, constitute negligence as a matter of law. For additional information on how this principle would be applied in the school negligence context, please see our blog post, Paralyzed High School Football Player Settles School Negligence Case.