A school introduced digital reminders for library books and reported fewer late returns after one term. At first, the student council praised the reminders as the reason for the improvement. The librarian noticed two limits. The borrowing period had also been extended from two weeks to three, and classes had begun setting aside five minutes each Friday for students to check due dates. The council revised its statement. It said the reminders may have helped, especially for students who already checked messages regularly, but the school could not separate their effect from the longer borrowing period and the weekly check. A later survey added another detail: some students saw the reminder but still returned books late because they had left them at home. The message therefore solved an information problem, not every practical obstacle. The school decided to keep the reminders while comparing classes that used different check routines. The final report did not reject the first result. Instead, it replaced a single-cause claim with a narrower explanation and identified what evidence the next comparison needed.