Love the picture! Were you riding independently at 4 without an instructor by your side/holding a lead? Do you think a 5yo with average strength and balance can learn to ride safely?
At age 2, I would ride without someone beside me. Just my brother to hold onto, who was 2 1/2 years older than me. We liked to ride Pete the pony around the yard.
Yes, at age 4, I rode without anyone next to me. I was on my pony, my brother on his, and my mom riding her horse. And we'd go out and about on rides together.
For my first horse show when I was 4, I did halter, western pleasure, barrels, poles, and a few other events; by myself in the arena. Sure, I wasn't going breakneck speed, but I didn't need anyone leading me or holding me. I did it myself. I do remember my dad came and got me that afternoon so I could take a well-needed NAP!! A day of showing sure takes it out of you.
And I still have memories from that day.
And my grandma bought all the grandkids riding helmets when I was 5 years old and I've worn one since.
I guess I say its YOUR money and YOUR child. You do what you want, so long as the child enjoys it. If you want to continue lessons and your instructor is willing to work with a young one, more power to ya.