Assassination Classroom, Vol. 1 by Yusei Matsui

Meet the would-be assassins of class 3-E: Sugino, who let his grades slip and got kicked off the baseball team. Karma, who's doing well in his classes but keeps getting suspended for fighting. And Okuda, who lacks both academic and social skills, yet excels at one subject: chemistry. Who has the best chance of winning that reward? Will the deed be accomplished through pity, brute force or poison...? And what chance does their teacher have of repairing his students' tattered self-esteem?