Ah the next generation of Pilgrims! Hope things go as planned but be aware that, if everything
has improved by then, there will be a LOT of people walking next year - those that "missed out" this year and those that planned to walk in 2021 anyway as it's a Holy Year.
Either way you need to consider booking ahead at least for the first and, probably, last sections. The first because everybody is bumbling about and getting into the rhythm and the end because there will always be an influx of new walkers at Sarria.
Do you speak any Spanish? If not then use the intervening months to learn some - you don't have to be fluent. As you're still at High School perhaps ask your teachers if they can recommend a course or see if you can join in a class.
As always there is a mine of, often conflicting, information here on the site:
Trail runners vs boots vs sandals
Sleeping bags vs quilts/throws
Hiking poles vs being hands free
Hi tech vs back to basics.
Use the search engine first and don't be afraid to ask questions - we were all green once upon a time.
Don't know if you're female, male or whatever but do look at packing lists targeted at whatever your status is - Christmas might be a good time to start writing out a list of what you need. Remember the wise traveller's maxim: allow for more money than you think you'll need and take less gear than you think you'll need. If you get the second part wrong then the first part will make things right.
Have you ever been to Europe before? My experience is that young Americans can be nonplussed by the differences. If you're staying in conventional refugios/albergues be aware that they're usually co-ed (not the bathrooms although toilets can be). Don't expect "comfort stops" at frequent intervals out in the countryside - get used to peeing in the woods. The Spanish tend to eat late at night and, although they make allowances for foreign pilgrims, you'll need to adjust your habits accordingly. Unlike the US it is legal for 18 year olds to consume alcohol in bars and restaurants - that doesn't mean you have to!
Get some practice walking in over varied terrain (dead flat to exhausting hills) so you know your limits in advance and don't try to be too ambitious especially for the earlier stages.
Above all have FUN. In the end it's just a walk; you start in France and keep going until you end in Santiago, but what a walk
Buen Camino!