Tom runs fastest in his school.(保持原意）

Tom runs faster than any other student in his school.

在other后面，名词应该用单数形式。

tom runs faster than any other students in his school

Tom runs fastest of all his schoolmates.

不对吧，应该是....Tom runs faster than any other student in his school...吧

汤姆在学校里跑得最快.