That is simply the range for which the class is offered. In other words, kids going into these grades in the fall may enroll in this class. Most typically, children are grouped in double grade groupings, i.e. Ks and 1st, 2nd and 3rd, and 4th and 5th in the actual class. There may be some exceptions to this depending on enrollment, i.e., a drama class containing 3 grades.