My novel is about a school so has lots of characters. I have oullined the story and have a general flow. I have been told to expand my characters. All my characters sound same. Can anyone give me advice on what is best way to build the characters? Any advice will be very much appreciated.

The book is for young adults and the school is for 21 years olds. It is a global diplomatic school to solve world issues. Like a global peace corps.