This is the 7304th most frequent Russian word.
выступившие
"Выступившие" means "those who spoke" or "those who performed."
The word 'выступившие' is used as a participle describing teachers (учителя) who have spoken or have formally addressed something.
Выступившие учителя сделали важные замечания.
The teachers who spoke made important remarks.
Here, 'выступивших' is an adjective in the genitive plural form, modifying 'members' (членов совета) by describing them as those who have given speeches.
Обсудим предложения выступивших членов совета.
We will discuss the proposals of the board members who spoke.
In this sentence, 'выступившие' functions as a standalone description for representatives (представители) who spoke at a specified event.