What effects is the author trying to produce when he places the blowing of the mill whistle and the discussion of the mill in the middle of the Gibbs' children's morning?

Our Town pg. 14-15

MRS. GIBBS:
I'll come and slap the both of you,-that's what I'll do.
A factory whistle sounds.
The childen dash in and take their places at the tables.
Right, GEORGE, about sixteen) and REBECCA, eleven. Left,
EMILY and WALLY, same ages. They carry strapped schoolbooks.

STAGE MANAGER:
We've got a factory in our town" too-hear it? Makes blankets. Cartwrights own it and it brung 'em a fortune.
MRS. WEBB:
Children! Now I won't have it. Breakfast is just as good as any
other meal and I won't have you gobbling like wolves. It'll
stunt your growth,-that's a fact. Put away your book, Wally.