Defensive Postitioning

My question is this. In high school I had a coach tell us to play defense and push the players sideline or baseline. He also told us to plant one foot on the boundary line to take an automatic charge. He later told us that it would be an automatic technical if we did that. I asked my college coach and he said it was an automatic blocking call. One of my friends asked a high school ref (that isn't the greatest) and he said it would be an automatic blocking call too. But then my friend asked a different college coach who said it would be an automatic charge. Does anyone know the actual ruling on this? Any help would be greatly appreciated!!!! Thank you!