To find out how many students rode in each bus, we first need to determine how many students rode in the cars.
Since 4 students rode in cars, the number of students who rode in the buses is:
\[ 472 \text{ (total students)} - 4 \text{ (students in cars)} = 468 \text{ (students in buses)} \]
Now, since the remaining students filled 9 buses, we can find out how many students were in each bus by dividing the number of students in the buses by the number of buses:
\[ 468 \text{ (students in buses)} รท 9 \text{ (buses)} = 52 \text{ students per bus} \]
Thus, the answer is:
52 students.