What is the meaning of "looking after"?

[Frank Stern]

English Error, Elementary Level

ESL/EFL Test #20 "The interview", question 9

Q. Well of course the classes here usually have about thirty children on average. How do you manage as a teacher looking about that number?

(a) thirty
(b) a
(c) about

English Error, Elementary Level

ESL/EFL Test #20 "The interview", answer 9

Q. Well of course the classes here usually have about thirty children on average. How do you manage as a teacher looking after that number?

Correct entry: after
The error was: (c) about

You have found the error but your entry is incorrect.
Q. Well of course the classes here usually have about thirty children on average. How do you manage as a teacher looking on that number?
_________________________

What is the meaning of "looking after"

[Mister Micawber]

.
Look after = supervise, take care of.
.
_________________
Native English teacher at Mister Micawber's