Lvalio wrote: “It takes 7 (seven) years for the brain to achieve a degree of development capable of realizing and judging the world around it, with rare exceptions.
But after those seven years, the brain needs to experience the world before it starts judging it. So, we can say that a reasonable age for a person to become a Buddhist is 12 years..”
Actually, there is an account in the Tipitaka where a seven-year-old attained Arahanthood. I don’t remember the name of the sutta.