Younger son was in mommy and me at 2, but was a holy terror so I stopped after 1 session, determined to wait until he was old enough to go by himself. He next did tots rec at 3.5/4 yrs old for 1 session. At the beginning of the 2nd session I was told he needed to be on the Pre-Pre team, which was basically Boys Level 2. I waited a bit and moved him there in the middle of the session and he stayed on Pre-Pre team (2 days a week, 1 hour), then Pre Team (2 days a week, 2 hours) for the next year and a half, moving to the competitive team at Level 4 (3 days a week, 3.5 hours) when he was 6.
Older son was in rec classes at a different location doing 1 day a week on Saturdays and summer camps from the age of 5 to 8. He would come with me when YS was at practice for the years he was on Pre team. The summer that YS began Level 4, OS asked me almost casually, "Why aren't I on team?" And I almost slapped myself. See, I had been "told" to put YS on team, which was something I more or less expected. But it never entered my head to ask them if OS should give it a go as well. Part of that was that YS and OS were in separate schools at the beginning and we had to split up fetching, and chauffeuring of them because of my job. But by this time the kids were in the same school and I was doing all of the fetching and chauffeuring myself. So OS ended up on Level 4 at the same time as YS, even though he's two and a half years older.
So for YS the first competition was just shy of 2 years from when he started pre team and for OS it was probably less than 6 months from his first level 4 practice.