Final answer:
The number of students decreased by approximately 12%.
Step-by-step explanation:
To find the percentage decrease, we need to calculate the difference between the initial number of students and the final number of students, and then express this difference as a percentage of the initial number.
Percentage decrease = (Initial number - Final number)/Initial number * 100
Percentage decrease = (450 - 396)/450 * 100 = 54/450 * 100 ≈ 12%
Therefore, the number of students decreased by approximately 12%.