Perhaps you should try some spelling variations:
"improving overall performance series." » "improving average performance series.", "improving thermal performance series.", "improving governance performance series.", "improving overall performance studies.", "improving overall performance size.", "improving coverage performance series.", "improving rural performance series.", "improving federal performance series."
"improving school performance metrics." » "improving school performance measures.", "improving schools performance metrics.", "improving preschool performance metrics.", "improve school performance metrics."

You may be able to get more results by adjusting your search query.

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