Putting is one of the most important parts of golf for kids to learn right away. You need the technique, concentration, and lots and lots of practice. It will actually better your score in the long run.
You have to keep your original posture and follow through with your stance, stroke, grip, eye alignment, etc. One of the most common mistakes that grown ups and kids make is their position to the ball. You must hit the back of the ball and the center of the ball. This way you can follow through with a smooth stroke.
Be patient and take your time. It will all come with practice. Remember Practice, Practice, Practice!!!