When I was in high school I wrote a subroutine threaded FORTH for OS-9 on the TRS-80 color computer; it was 2000 lines of assembly code and it (almost) worked right the first time.
When I was in junior high school I wrote a fully functioning perl on the TI-80 graphing calculator. It was about 200 lines of code, and it (almost) worked right the first time.
When I was in high school I wrote a subroutine threaded FORTH for OS-9 on the TRS-80 color computer; it was 2000 lines of assembly code and it (almost) worked right the first time.