Jade was nervous to join in the excursion right from the beginning, but when Lucius and his cohorts came to her and Desmond, there was no way they could reject them. She would not be given any special permissions to avoid participating in the work-studies, and it was unlikely that anyone would take her in.
Since Desmond would not join anyone without bringing her along as well, he also would have been left out. That would have meant the two of them would be doing the work alone and that would present a lot of risk. Though uncommon, it was not unheard of for senior students to go missing or die on the work-studies. That was why only the senior class participated.