They never tell you what 'the age of responsibility' is. It allows for comments and anecdotes like these:
w06 7/1 pp. 29-30 pars. 15-16 Youths, Make It Your Choice to Serve Jehovah
Young ones, please do not imagine that by postponing baptism, you avoid accountability. When you have reached the age of responsibility, you are answerable to Jehovah for the way you act whether you are baptized or not.—Romans 14:11, 12.
16 Numerous Witnesses around the world feel that their decision to get baptized when they were young helped them greatly. Take as an example a 23-year-old Witness in Western Europe. He recalls that getting baptized at the age of 13 motivated him to be careful not to be swept away by “the desires incidental to youth.” (2 Timothy 2:22)
w92 3/1 p. 27 Pursuing a Goal Set at Six Years of Age
In the summer of 1946, I was baptized at the international convention in Cleveland, Ohio. Although I was only six years of age, I was determined to fulfill my dedication to Jehovah. That summer I served as a pioneer for the first time. I remember one morning placing 40 magazines with people seated at The Plaza in San Diego, California. My being tiny and talkative had a lot to do with it, I’m sure.
w88 3/15 pp. 14-15 Trust in Jehovah Leads to Dedication and Baptism
Baptized at What Age?
20 Jesus’ words at Matthew 28:19, 20 show that it is those who have been made his disciples that should be baptized. Hence, it follows that no infant or small child could meet the Scriptural requirements for baptism. An infant could not exercise faith in God’s Word, in God the Creator, and in his Son Jesus Christ. An infant could not understand that the holy spirit is God’s active force; nor could it repent of past sins and make a solemn vow to do God’s will.
21 But it seems that some among Jehovah’s people have gone to the other extreme. Many Christian parents let their children wait until they are in their late teens before broaching the subject of baptism. Time and again, we hear of youngsters making a valid dedication solely on their own initiative. For example, the preteen son of an elder sincerely wanted to get baptized. So his father had three other elders discuss with the youngster the questions designed for those contemplating baptism. Their conclusion was that, though quite young, he qualified to be baptized as an ordained minister of Jehovah God. Why, attending the Pioneer Service School in the Bahamas recently was a ten-year-old baptized girl, the daughter of two full-time ministers!
Obviously, ten and six year olds aren't counted as 'small children under the age of responsibility.'