Answer:

ISTOO

AnswerCrossword Clue
ISTOO"The rent ... damn high!"
ISTOO"This ... much!"
ISTOOSchoolyard retort
ISTOO"Life ... short..."
ISTOOPlayground retort
ISTOO"One enemy .. much": Herbert
ISTOO"The world .. much with us": Wordsworth
ISTOOInsistent comeback
ISTOOPlayground assertion
ISTOOKindergarten rejoinder
ISTOOPlayground rejoinder
ISTOORejoinder to "Ain't!"
ISTOOChildish comeback
ISTOOChildish rejoinder
ISTOO"Life ... short ..."
ISTOORecess retort
ISTOO"This ... much to understand"
ISTOOKid's comeback
ISTOOPlayground rejoinder to "Ain't!"
ISTOO"Life ... short"
ISTOO"The rent ... damn high!" (2010s NYC political slogan)
ISTOO"One enemy ... much.": Herbert
ISTOOImmature retort
ISTOOInsistent words from a sandbox
ISTOOHalf a playground exchange
ISTOO"Ain't neither!" retort
ISTOOPlayground rebuttal
ISTOOPlayground reply
ISTOO"Ain't neither!" reply
ISTOOChildish retort
ISTOO"Ain't so!" reply
ISTOO"How much .. much?"
ISTOO"Not so!" reply
ISTOOCry of insistence
ISTOOInsistent cry
ISTOOResponse to "Not so!"
ISTOOPlayground comeback
ISTOOIt ... much to ask
ISTOO"That ... much for me"
ISTOO"This ... much"