The two school modulars promised to William Reid school in Calgary-Elbow jumped past six other projects deemed by school officials to be higher priority.
Days later, on Oct. 27, Dirks won a hotly contested byelection race.
Dirks has refused in question period to say why he made the decision to bypass higher priority schools and has refused to talk to reporters outside the house.
Opponents say the decision was unethical electioneering and abuse of ministerial authority, putting the lie to Prentice's promise to return government to integrity following the scandals of the Alison Redford era.
Prentice, however, told reporters that while priority lists for modular classrooms are important, they are not written in stone.
"His (Dirks') ministerial responsibility involves exercising judgment to make those kinds of choices at the end of the day," said Prentice.
"There are no lists that are absolute.
"(Dirks) was aware for some time of the pressure in that community for modular schools and there's pressure everywhere in the province.
"He chose to take action."
Prentice said he understands why critics feel it was unfair to make the announcement during a byelection, but said: "I'm not hearing anyone suggesting that it was the wrong decision in the sense that modular schools are needed in that location.
"It has been one of the hardest-hit communities in the entire province from the 2013 floods."
Prentice hand-picked Dirks, a former chairman of the Calgary Board of Education, to be in cabinet when he was sworn in as premier two months ago.
Prentice was criticized for blurring the lines between politics and government during the byelection by making funding announcements for health care and for schools. Dirks also showed up in Calgary to have his photo taken at numerous sod turnings for new schools.
NDP Leader Rachel Notley asked Prentice in question period Wednesday to bring in legislation, as has been done in other provinces, to ban those kinds of announcements and events during campaigns.
Prentice didn't answer in the house, but later told reporters he won't do it.
"(Dirks) was the minister over the course of the byelection and had responsibilities to exercise as the minister. He exercised them doing what he was supposed to do, which was to listen to Albertans," said Prentice.
In the coming days, Prentice will introduce legislation to eliminate questionable contracts, generous severance payments, and ensure accountability and integrity in government.
Opposition parties have called on the ethics commissioner to investigate Dirks' behaviour.
NDP Leader Rachel Notley said Dirks has sent a disquieting message.
"We're going to have this continued debate that he can't be trusted to make decisions in the public interest and for the best interests of Alberta students because he has so clearly allowed inappropriate considerations to impact how he makes these decisions," said Notley.
Wildrose Leader Danielle Smith said, "I don't think Albertans like the appearance of it. I don't think it passes the smell test, and it certainly is not the kind of standard that we expect our education minister to live up to."
Liberal Leader Raj Sherman told the house Tuesday that the Prentice government is beginning to look like the Redford one.
"Isn't this the same sort of political trickery that characterized previous PC governments?" said Sherman.