What are you classifying as "childhood?" Anyone below the age of 18 (isn't it 16 in the UK)? I have fought and beaten a man in his 30's when I was 14 years old, and I know others who have done the same as young as 12. There was even a video of Katt Williams getting beaten up by a 12 year old that went viral a few years ago. Are you counting high school students as "children?" Because people are usually still in that high school mentality for the first few years after graduating. Fights happen on college campuses between people who are adults by any definition.
As a I told Kung Fu Wang, if by "sparring," he means what's in the videos he posted, then yeah, I'll put them against an experienced untrained fighter. But I won't do the same for someone who has only done sparring by the dictionary definition of it, which describes the typical kumite at a karate dojo or equivalent elsewhere.
That's a very general statement. Do all TMA'ists have real fighting experience? No. Do most? I don't know. Do some? Without a doubt.