I recall, in high school, we were writing a disassembler for a custom weird assembly language which was written by one of the school's graduates a few years prior to that... and we had to use this assembler as a language of choice :) That's high school! And it was quite fun. These days, many CS grads/post-grads know tensorflow and other flashy high level stuff while having very vague understanding of how things actually work at the lowest level (source: interviews).