My all-time best in junior year was around 2:10-2:12, and I ran a 4:46 for 1600m at the end of season.
Sr year was much more speed-focused, where I ran several 4x400m legs in 55 and down to 54.high, and my best 800m of season was a 2:06 with a really bad fade at the end due to poor pacing, effort, or just not having anyone to run against in a sparse field. I passed my even harder fading teammate and instead of holding pace, slowed down, probably could have run 2:04/5.
Summer after high school I ran a 37sec 300m trial solo, and since then I've continued to chip away at my short sprint times to the point I'd probably lower my ceiling for 300m /400m to 35/51 sec, and I think I'd be able to go even faster than that.
all this to say, I think you could get to 55-56, as I think it's pretty achievable for most young men, but getting under around 54x is where it starts to be more difficult. Depends how developed you are, are you coordinated, muscled, lean.... chances are you have a couple of those 4 parameters to develop, and then add some event specific skills, seems to me 55 seconds is doable.