I believe Sean's solution has an extra unnecessary step.

If to use the filtering subquery in the JOIN it may provide sorting criteria as well.

Then CTE query may be excluded:

SELECT *

FROM @mySampleTable s

INNER JOIN (SELECT CaseID, MAX(CreatedDate) LatestUpdate

FROM @mySampleTable

GROUP BY CaseID

HAVING MAX(StudentID) != MIN(StudentID)) fs ON s.CaseID = fs.CaseID

ORDER BY LatestUpdate DESC, CreatedDate DESC