The drop kick comes at 1:32 in the video:
Pulaski Academy Onside Kicks vs Cabot - Sept 9, 2011 - YouTube
Per rules 2-24-5/6 and 6-1-2, I have no problem with using a drop kick for a free kick, and the drop kick occurs at the free kick line.
Where I am curious is the first player running up, picking up the ball from the tee, and backward passing the ball to the kicker. I ask only because I have never seen this before and would like feedback.