There are actually two climaxes in the story: the turning point and the point of highest interest. The turning point occurs, as the previous editor noted, when Paul and the reader realize that no amount of money can stop the house from whispering. The incident that makes this idea clear is the mother's reaction to the news that she'll receive a thousand pounds for five successive years on her birthday. Instead of being content, the mother requests that she receive the entire sum of money at once, and the house intensifies its screams for more money, as the mother wants more things: new furnishings and luxuries as well as an expensive education for Paul. At this point the reader knows that Paul's winnings will never satisfy his mother.
The point of highest interest in the story comes later when we see Paul feverishly riding his rocking horse to determine the winner of the Derby. Here the suspense is very high as we see Paul circumvent his mother's attempts to take away the horse and send Paul to the seaside. We want to know if Paul will be successful, if winning the Derby will have any effect on the house, if it will take too much toll on Paul's health, if the mother will change. As the mother rushes home from the party, the suspense builds as Paul is shown frenziedly riding his horse, and announcing the winner "Malabar" as he falls unconscious with brain fever.
The conflict in the story is complicated. It is more an internal conflict caused by external factors. Paul desires his mother's love and happiness. We know the mother equates money and happiness, and this connection is seen in the house's whisperings. Paul is willing to sacrifice himself to make his mother happy, much like today people will work themselves to death to provide more luxuries for their family. But the truth of the matter is, the more people have--such as Paul's mother--the more they want. Being happy requires changing values and priorities. So the conflict can be defined as man fighting a losing battle against human nature.
Another significant turning point in the short story "The Rocking Horse Winner" by D.H. Lawrence is later on, when the boy starts to behave in an out-of-control sort of way. Even though this happens right at the end, this seems to mark the point where the mental and emotional strain has become so unbearable that the boy's mind begins to crack, and his personality to unravel. He has enjoyed the competition and ambition of winning money on the horses up until now, but I think he reaches a point where he knows that enough will never be enough, but he can't stop 'riding' the business of gambling. This is signified by the demented crazy way he rides his rocking-horse at the end, spurred on like a riderless horse in a race - with no destination.
In Lawerence's story "The Rocking Horse Winner" the turning point comes when the boy, Paul's mother learns that he is able to provide the family with money and has a way of winning it. Up until his mother learns his secret the boy has been accumulating money buy riding his rocking horse as hard as he could. It was physically draining on him, but tolerable. Once his mother finds out that Paul has the ability to make an unending amount of money she increases her lifestyle to a greater level with each sum he wins.
The conflict is that Paul must continue to earn more money, endangering his own health, in order to make his mother happy and to try and obtain his love.