Perhaps you should try some spelling variations:
"improving rural performance series." » "improving rural performance metrics.", "improving rural performance reviews.", "improving rural performance review.", "improving pupil performance series.", "improving thermal performance series.", "improving overall performance series.", "improving urban performance series.", "improving social performance series."
"improving school performance issues." » "improving school performance measures.", "improving school performance based.", "improving school performance size.", "improving schools performance issues.", "improving preschool performance issues.", "improve school performance issues."

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (("improving rural performance series.") or ("improving school performance issues."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving rural performance series.") OR ("improving school performance issues.")).
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• Adding a wildcard symbol may retrieve word variants: (("improving rural performance series.") or ("improving school performance issues."))*.