reading all these responses, I guess it really does depend on how aggressive the horse really is. For me, when I deal with horses, I only put at much pressure on him as he/she does to me. Don't go beyond the limits that he's set <-- if that makes any sense.
My horse has done this many times in the past when I first got him. I always have my carrot stick with me when I lunge him and as soon as he charged at me i'd raise my stick and firmly swing the rope over top of his bum and send him back out to whatever gait he was in. If he ever cut in on me i'd swing the rope over his withers or use the other end and tap his withers with it until he gives in.
Timing is important too, pressure and release.
Hope this helped, and good luck!
OH! And also, never let that horse get away with it. EVER! End on a good note. But make sure he knows what was done.. was wrong. :)