Surely the following is an easier way to accomplish this...

SELECT PR.id, PR.ProfessorName, ClassName, ClassYear, ClassSemester

FROM Professor PR

LEFT JOIN

(

SELECT ProfessorID, ClassName, ClassYear, ClassSemester

FROM Class

WHERE ClassYear>=2011

) SQ ON SQ.ProfessorID = PR.Id

WHERE PR.HasTenure = 1