...in/from Raffles Primary School

[Tan Elaine]

Jack, in/from Raffles Primary School, is an amiable boy.

Which word in bold should I use?

Thanks.

[SirGod]

* Not a teacher

Both could work.

Jack, in Raffles Primary School, is an amiable boy. (this means he is (behaves as) an amiable boy only in that school, outside it he is not amiable anymore - probably not what you are looking for)

Jack, from Raffles Primary School, is an amiable boy. (this means that he belongs to that school, he learns there - probably what you are looking for)