Ditto. In my day it was called “finishing the 6th grade.” Technically every move up in “grade” is, by definition, an “grad-uation,” but ceremonies are reserved for conferral of credentials (a diploma). This “6th grade graduation” stuff is part of the “participation trophy” generation.
By the time kids graduate from high school, they’ve already “graduated” from pre-school, kindergarten, sixth grade, and junior high. When it comes time for the high school ceremony, it’s “old cap-and-gown.”