While there is no official "highschool technical gamer" version of Grand Theft Auto V (GTA 5) , you are likely referring to a popular highly-compressed fan-modded version of the game often distributed in small files (sometimes as small as 18MB to 500MB).
While many third-party sites offer extremely compressed RAR files (sometimes as small as 2.5 GB), there is no official release of this kind. You should be cautious with these files for several reasons: Extreme Content Removal gta 5 by highschool technical gamerrar
Keep modding, you crazy tech wizards. The industry is watching. While there is no official "highschool technical gamer"