The question is asking to explain the message the poem is saying but i don’t know the poem so may i please see it so i can try to help.
Ir because Ir conjugated is
Yo - voy
Tu- vas
El/Ella/Ud. - va
Nosotros - vamos
Ellos - van
Ir is an irregular verb.
I’m no Mexican, but I think, The answer is Tristes.
Las Estudiantes is plural. So triste is plural. Sometimes just by saying something out loud will indicate if it makes sense. But if it was la chica Esta Tristes, that won’t make sense. Try la chica Esta Triste, that’d make sense. Hope I helped!