where the graduates will go when they graduate from school.这句话单独存在讲不通,这是一个名词从句,可以做主语、宾语、表语.
例如：Please tell me where the graduates will go when they graduate from school.（宾语）就成立了.或Where the graduates will go when they graduate from school is not decided yet.（主语）
What they are worried about is where the graduates will go when they graduate from school.（表语）
若想单独存在,可以改为疑问语序：Where will the graduates l go when they graduate from school?