This query will give you students who have an F, but at least a 50%.  (Used by a site to invite students to Tutoring).

LIST STU GBU GBK STU.NM STU.SG GBU.CMK GBU.CSC GBK.NM TCH.TE GBK.PD GBU.D2 IF STU.GR = 10 AND GBU.CMK : F AND GBU.CSC >= 50

After Fall Term is over, you will need to add in a date to the IF Statement, to make sure you get current gradebooks.