Jeremiah 12:3
But thou, O LORD, knowest me: thou hast seen me, and tried mine heart toward thee: pull them out like sheep for the slaughter, and prepare them for the day of slaughter. But thou, O LORD, knowest me: thou hast seen me, and tried mine heart toward thee: pull them out like sheep for the slaughter, and prepare them for the day of slaughter.
The Lord knows each person, sees each person, and tries the heart to test whether it is turned toward Him in loyalty, faithfulness and devotion. He weighs every motive and discerns the thoughts, intents and purposes of the heart. The verse is a declaration of confidence in God's complete knowledge of a person and of the motives within the heart. The request to pull them out like sheep and prepare them for slaughter is a prayer asking God to judge those who oppose the speaker, not a description of students as appointed for slaughter.
The day of slaughter is the coming time of God's burning wrath in the seven last plagues. God draws a covering over His people to shelter them in that time, and Satan tries to keep them from receiving it until the sealing is past. Everyone should be able to make the verse's claim by putting away all selfish desire for distinction and every unholy ambition, bringing every human suggestion to God and trusting the Holy Spirit's guidance, so that this searching finds the motives pure and the heart true toward God. Students in particular should seek God's counsel with open hearts before choosing a course of study, since God weighs their motives and knows whether their choices are directed toward Him.
Children must get ready to stand in that coming day, which requires feeling acceptance with God now, calling upon Him and making peace with Him, without resting a moment lacking that assurance. Those who stand in that day will be saved in the kingdom and enjoy the beauty of the earth made new. Getting ready means not loving this world and not loving the wicked, but loving God and loving those who bear His image.