Wow must take one hell of an education to figure that out and if it were accurate I would probably leave it alone, unfortunately, it isn't so I won't.
Other than the two half baked Italians demonstrating the art of spear tackling for the ref the majority of the cards have been for players falling into tackles so while it is neat to be able to give the glib response "Here's a hint don't tackle at head height" it is very inaccurate as they are not tacking at head height but rather stomach to chest height.
What are the stats to date 26 yellow and 7 red cards handed out in the pool games now you can and do try to argue that these offences have been in place for years which is true however for some reason they waited until rugby's showcase event to enforce them and then treated every offence as the worst case, if they keep this up the winner will be the team with the most players left on the field at the end of the day which as I have said is detracting from the sport.
As an aside, we were taught to ensure your tackle was below nipple height, preferably wrap the elbows up to prevent offloads and encourage dislocation of the ball.