YOU SAID:

I was the biggest boi in the class from the 1st grade untill the senior year at highschool

INTO JAPANESE

１年生から高校１年生までクラスで一番ボイでした

BACK INTO ENGLISH

From first grade to high school first grade was the most boy in the class

INTO JAPANESE

１年生から高校１年生までがクラスで一番少年だった

BACK INTO ENGLISH

From first grade to high school first grade was the youngest in the class

INTO JAPANESE

１年生から高校１年生までがクラス最年少

BACK INTO ENGLISH

1st year to 1st year high school is the youngest in class

INTO JAPANESE

1年生から1年生までの高校はクラス最年少

BACK INTO ENGLISH

High school from grade 1 to grade 1 is the youngest in class

INTO JAPANESE

1年生から1年生までの高校はクラス最年少

BACK INTO ENGLISH

High school from grade 1 to grade 1 is the youngest in class