Spend your own time in prayer and in the Word. Don't just read the Bible to prepare for your students, read it for your own enjoyment. And don't always think only of your students when the Word is showing you something. God still speaks to workers, too, and may be speaking to you and you only. Don't feel you have to teach your students everything God is teaching you.
Integrity comes from the mathematical term, integer .
An integer is a whole number. Integrity means you are wholly devoted to something. Be wholly devoted to God - not your ministry. The ministry will come when you put God first and love Him most. Go to Student Ministers' conferences and have friendship and accountability groups among your peers.