Most scholarships - but not all - are available to seniors only.  Some are available from 8th-12th grades with all kinds of variations between these extremes. 
When CHS advertises a scholarship on this site, it also appears in the Scholarship Sort file, a page where you can see at a glance:  the application deadline, whether you have to go to a particular school or enter a particular major, whether it's set aside for minority students, whether other students may apply (other grades besides seniors), and whether it is considered a local scholarship.