ya, from what my parents told me, I was 2.  When I coached, there were some really young ones.  Youngest I coached was 3 1/2,  but there were a few a little under 3 that snuck in.  For park tho, I taught a 6 year old girl to do a rail while holding my hand, but they mostly liked hitting the little jumps and watching me switch up or front 2 haha.  One kid ripped tho, he didn't do park, but he would cruise going about 45 and fully in control