Here is a possible seating chart for 21 students in a classroom:

Row 1: Student 1, Student 2, Student 3, Student 4, Student 5 Row 2: Student 6, Student 7, Student 8, Student 9, Student 10 Row 3: Student 11, Student 12, Student 13, Student 14, Student 15 Row 4: Student 16, Student 17, Student 18, Student 19, Student 20 Row 5: Student 21