Complex sentence: Important changes included an assurance that every resident has access to an education, a pointed response to "massive resistance," an anti-integration movement during which some school systems opted to shut down rather than admit black students.
Split into simpler sentences: Important changes included an assurance that every resident has access to an education. The latter was a pointed response to "massive resistance," an anti-integration movement during which some school systems opted to shut down rather than admit black students.