I apologise for the bluntness.
What's wrong with 10 speed?
You're still junior, don't stress? Your advantage will come from power output. You aren't going to win an U19 race with one extra cog.
Otherwise the suggestions are good. If you want 11 speed. Find someone that will make a 45t front ring.
Here's another tip. What are the neutral spare wheels? If they're 10 speed. Run 10 speed.
...10 speed makes the most sense for every amateur bike racer.
Nothing is wrong with 10spds, I use old 9spd on the TT. The team bikes have the Shimano 9000 group. While a front 52X38 is available a 45T is not.
Neutral spare wheels are both / all 10spd and 11spd and 14T in the SRAM and Shimano cars. Last year the 10spds were used on the 11spd setup for racing where they do not allow blocked gears. For other races you can block the gears out. So a neutral 10spd will work when needed.
I thought there might be a better setup - like a 14-27 alloy 11spd freewheel.
P.S. I'm the parent, not the rider.