After completing his teacher training, John was placed in a pool post as a qualified substitute teacher.
完成教师培训后，约翰被安排在一个备用教师库中，成为一名合格的代课教师。
The school district uses pool posts to ensure there are enough teachers available during teacher shortages.
学区使用备用教师职位来确保在教师短缺期间有足够的教师可用。