My best driver was 15 when he started in a shifter.
He was super mature and laser focused on everything it took to be the best driver he could be. He actually won the money to buy the kart from winning the F1 Sim Championships the year before so he had a very clear idea of what he was getting into. He also had the confidence to approach me on his own and ask to drive for me because I was running a series he wanted to be involved with.
Now if it was my kid….
No way. Even though she’s smart and confident I would want her to spend a bunch more years getting good at clutch karts before moving up (quick disclaimer: my 15-year-old plays volleyball, she likes driving karts but doesn’t race). Bad habits with driving are easy to form and hard to get rid of. Learning how to drive smooth is just plain hard when you have to make 50 shifts in a minute and a half lap and you’ll never be truly fast if you’re not smooth as baby do-do. Also, like any sport karting requires a bunch of practice if you want to be good. I don’t have any idea what your finances are, but I bet if you’re asking this question you’re not on the path where your kid will be running Indy Lights like these two.
Unfortunately being a dad sometimes means holding your kid back so they can get the experience they’ll need for the future. If your son is determined to race shifters he’ll find a way to do it regardless of what you say. But, be aware that running with the “fast guys” at your local track on a practice day and being competitive anywhere it counts are two different things.
I’m sure you’ll make the right decision but I would discourage moving him up after only one season in junior karts unless he has the motivation to not only drive a shifter but also wrench and help pay for it.