I'm glad your school did that. My mom had to fight against my elementary school because they wanted to keep me back a year in kindergarten because I wasn't mature enough. Likely, I was just bored. I went in to school reading and could do basic arithmetic already (even knew some basic multiplication), but they wanted to keep me back. Also happened going into middle school when I tested out of prealgebra (the accelerated math class they offered) but the new principal wanted to keep everyone the same. Thankfully I had good elementary school teachers through 3rd grade who recognized this and gave me challenging stuff instead (never made me read what the other kids read, harder msthh practice sheets, etc).