What event was the turning point, or climax, of the story Wednesday Wars?

I believe that the turning point or climax of the story
occurs in May, when Holling returns home after taking a tour of the city's distinctive
architecture with Mrs. Baker, and spending time with her at St. Adelbert's, praying for
all the people in his life. With all the elements of his awakening to others in place,
he enters his house and feels its emptiness, understanding that the biggest part of the
void there is because his sister is gone, and he loves her. Holling
says,

"Maybe
the first time that you know you really care about something is when you think about it
not being there, and you know - you really know - that the emptiness is as much inside
you as outside you."

By his
own admission, this is the moment when he knows that he really does love his sister, and
his love is unselfish, because he does not know "if he want(s) more for her to come back
or for her to find whatever it (is) that she (is) trying to find." When Holling's sister
calls to say that she needs help that night, Holling, who used to be a passive actor in
his own life, takes positive action, standing up to his father and doing what is
necessary to get her home safely. Through his experiences over the year, and with the
help of Mrs. Baker and others who support him in his development as an honorable and
courageous human being, Holling now has the maturity to be a giver instead of a taker,
and he is able to prove it by saving his big sister with reasoned and effective support
that is both practical and emotional (Chapter 9).