Children of 2 and 4 years old can be treated - by the time they are 6 years old the treatment will not actually cure them in the same way. This is because a child under age 6 has neuralplasticity that an older child does not, and is able to create neural pathways to not stutter. I'd strongly recommend you read my post in this thread about my experiences - and I hope you find it helpful. And I agree with you about NOT bringing you child's attention to it - my son never actually knew he stuttered and now he no longer stutters he doesn't know he used to stutter. This is because he was treated purely in a reward context - his stutter was never actually pointed out to him - and I completely agree, pointing it out would have been a disaster.