Marty Walsh’s speech to the Boston Municipal Research Bureau Tuesday was supposed to focus on a new initiative aimed at boosting the city’s middle-income housing stock. But while the mayor discussed that program briefly in his speech at the Seaport Hotel, he spent more time defending his stewardship of public education in the city—a response, it seemed, to yesterday’s protest of proposed cutbacks in the Boston Public Schools.

“At $1.013 billion, we spend more on Boston Public Schools than ever before,” Walsh said, as an assortment of Boston-area business leaders looked on. “Education funding is [as] large [a] portion of our overall budget as it’s ever been—more than any other city department combined.”

“This year,” Walsh added, “I proposed a $13.5 million increase. That will make it nearly $90 million in new funding since I took office … The Boston Public Schools spend more per student than any other major district in the United States.”

Then came the caveats. State education aid has declined, the mayor said. Labor costs have skyrocketed. And the current BPS infrastructure can accommodate 93,000 students, even though enrollment has dropped to 57,000.

What’s more, Walsh added, money Boston is forced to allocate for charter schools continues to grow—the result, he said, of a “broken charter-school financing system” the state Legislature needs to fix.

(All of which explains why—despite the funding increases touted by Walsh—the Boston Public Schools face a budget deficit of up to $50 million dollars for the coming fiscal year.)

Then, Walsh seemed to address the students who walked out of the Boston public schools yesterday to protest on Boston Common, even though he never actually used the words “protest” or “walkout.”

“I know uncertainty in the budget process causes great concern, and I appreciate that people care deeply about their schools,” Walsh said. “I care deeply about them as well. That’s why our proposed budget increases per-student funding, even while adding prekindergarten seats and making advanced work curriculum available to more students.”

And yet, he continued: “The truth is, the Boston Public Schools have not paid the price for our growing charter assessments—but every other city department has. It’s a structural tension on our budget that is steadily building to a crisis.”

To deal with that crisis, the mayor says he needs flexibility—from BPS teachers who are poised to begin a new round of collective bargaining, and from parents and students whose routines may be disrupted as the city tries to bring school infrastructure in line with current enrollment.

“We are prepared to make significant capital investments in our schools,” Walsh said. “But they only make sense if we can do a better job matching our facilities footprint with our student population.”

After yesterday’s protests, Walsh suggested that the participants acted on the basis of bad information, and at the behest of outside groups. On Tuesday, he stood by that characterization.

“They had bad information,” Walsh told WGBH News. “It’s easy to be critical from the outside, and these are some community leaders and elected officials being critical from the outside. But they know the situation here.”

The Boston School Committee is slated to vote on the proposed budget on March 23.