Rajkumar, As your question doesn't include the stream or standard of education (Class) for which you are interested in, so, here is a list of few popular top schools in Gorakhpur according to many surveys and reviews from various organizations and students:--

ARMY PUBLIC SCHOOL

JAWAHAR NAVODAYA VIDYALAYA

PILLARS PUBLIC SCHOOL

LITTLE FLOWER SCHOOL

G N PUBLIC SCHOOL

AIR FORCE SCHOOL

St JOSEPH SCHOOL

KENDRIYA VIDYALAYA

GD GOENKA PUBLIC SCHOOL

Hope this helps you.