Hide child pages from menu tree
If you don't need the case studies to appear in the secondary nav/sidebar menu, you could try using the Path Breadcrumbs module to set custom rules for any of the following scenarios:


all "Case Study" content resides in a fixed hierarchy
"Case Study" content with a specific tag goes in a fixed hierarchy
"Case Study" content breadcrumbs are defined by url alias/path that reflects parent pages.


The module is rather flexible in the rulesets you can define.