Maybe around 2nd grade with the piper computer which was a small rpi based laptop that you built. I switched fully in 5th grade when my windows install broke. A few months before that I switched on my laptop when my math teacher reminded me about it. I Have rarely used windows since but for a few months I used a Mac laptop. My linux laptop (Dell xps 13 7390) I had was hidpi, kind of slow and died quickly and the m1 Mac hardware was just plain better (this was close to when the 2020 m1 Mac came out so no asahilinux). I have used pop, manjaro, arch and alpine Linux. I have been using it for a few years now and never plan on going back to windows though I do occasionally use macOS for nonfree/closed source apps. When I first switched the only game I played was Minecraft which worked just as well as windows. Now almost all the games I play are free software like Minetest and super tux kart.