* For disciplinary reasons: "Saturday school is being held because some students haven't been following the school's rules. It's a consequence for things like excessive absences, tardiness, disruptive behavior in class, or not completing assignments."
* For academic support: "Saturday school is offered to provide extra help for students who are struggling in certain subjects. It's a chance to get extra tutoring and catch up on missed work."
* To make up for missed school days: "Due to [reason, e.g., snow days, unexpected closures], we've lost some school days. Saturday school is being held to ensure we still cover all the required curriculum."
* For enrichment activities: "Saturday school isn't a punishment; it's an opportunity to participate in enriching activities like [e.g., art workshops, sports training, academic clubs] that aren't offered during the regular school week."
* For exam preparation: "Saturday school sessions are being held to help students prepare for upcoming important exams. They'll provide review sessions and practice tests."
To give a good explanation, you need to know *why* Saturday school is happening in your specific situation. Then, tailor your explanation to that reason, being clear, concise, and fair.