The words and phrases below share a certain quality that has to do with school. Can you determine what it is?

LOANSHARKING
LOOK WHO'S TALKING
LONDON FOG
LOLLYGAGGING
LOAD-BEARING

HINTS:
#1: It has to do with a certain subject taught in school.
#2: The subject is arithmetic.

Answer:

Each word or phrase begins with LO and ends with NG. The word LONG is divided by the other letters in the word or phrase, thus suggesting LONG DIVISION.

Credit: LA Times Crossword
Sylvia Bursztyn and Barry Tunick
LONG DIVISION