Yes I believe students (middle school and high school) can be leaders and are often great examples. In two recent back-to-back services I witnessed middle school and high school students being leaders.
First the middle schoolers; at part of our worship service we spend some intentional time welcoming our guests, really just a time of informal greeting of those people who are sitting around us. Usually the crowd waits for the on-stage leader to instruct them either to remain standing or take their seats. In this particular service however, before instructions could be given, a group of students who always sit in the first few rows of the center section began to sit down. The whole congregation followed.
In the next service the worship leader had chosen to have the congregation be seated during the singing of a song. It was a powerful song with powerful words that reminded us of what a wonderful Savior we serve and what He has done for us by His sacrifice. As the song begin to build, one student stood to her feet and began to worship with hands raised. The whole congregation followed.
I am reminded of the scripture in I Timothy 4:12 where the writer encourages a young leader by saying:
No one should despise your youth; instead, you should be an example to the believers in speech, in conduct, in love, in faith, in purity.
In that encouragement I am reminded that we should not flippantly disregard the actions of youth because they are youth. That encouragement also challenges the youth to be examples to all...that is quite a challenge.
As the older generation I should look to see where God is leading no matter who is taking point. I believe I am also commanded to provide training opportunities for students so they will be better prepared to lead.