Final answer:
The student's question is not clearly defined, but the provided information indicates that improvements in student performance may be due to self-selection and intrinsic motivation, not just changes in school day length.
Step-by-step explanation:
The question seems to reference the idea of changing a 'default learning mode period', which could relate to policies or practices in educational settings. However, the provided information discusses the difficulty in attributing the improvement in student performance to specific changes due to the simultaneous implementation of two different policies: a shorter school day and a motivational contract. This suggests that changes to the learning environment or schedule may not be solely responsible for any observed improvements, as factors such as self-selection and intrinsic motivation of students can significantly influence the outcomes. Therefore, without clear evidence, it's not possible to determine if changes to the default learning mode period alone would lead to improvements.