My mom told me that she had me tested for public school kindergarten, but I didn't get in. I was at my daycare for a good 3 or so weeks before my mom figured out that the teachers realized I was ready for kindergarten and just had me switch classes. So I started K5 (which was the only kindergarten level that existed at the time -- I'm 29 now) at age 4. And I graduated high school and started college at age 17 -- not a huge difference and one I'm grateful for now.
My daughter is smarter than me -- and I can admit to that! LOL She was reading and writing around 3 1/2; and she out-thinks me in a lot of areas I'm not prepared for most days. I enrolled her in a preschool in a 2 1/2 year old program where they went for 3 hours in the morning. Then at age 3 she went to the next level of preschool. This will be her third year at the school. They use the Waldorf method there and I think that's part of why I like it. Yes, there is structure, but there is a lot of time for free-play. My daughter BEGS to stay for the afterschool program (called Lunch Buddies and Afternoon Adventures) and I'm okay with that, but we limit it to about 2 days a week. From day 1 of school my daughter was the one who cried when I picked her up to go home; never when I dropped her off.
It is amazing how it's all changed. By the time my kid finishes high school she'll have been school for 15-16 years -- that just seems crazy to me!