* Minimum instructional time: Most schools have a minimum number of instructional hours or minutes required to constitute a full school day. Falling short of this threshold might mean the day isn't considered a full school day for attendance purposes, state funding calculations, or other metrics.
* Scheduled classes: Simply being present at the school building isn't enough. The day must involve participation in the regularly scheduled academic curriculum.
* Exclusions: Days cancelled due to weather, emergencies, or professional development are generally *not* considered full school days. Early dismissals due to unforeseen circumstances might also be partially counted, depending on school policy.
In short, a "day of school" is a day where students are engaged in a substantial amount of their typical academic program, as defined by the school or district.