This is actually a very easy equation: A + B = C.

A) A notable (if insufficient) portion of the tax payments made by Buffalo residents goes to support the city school district.

B) Buffalo Mayor Byron W. Brown represents all of those taxpayers.

C) He should be more than slightly involved in ensuring that taxpayers’ investment is well-placed.

Yet, he isn’t. Brown and his aides go to lengths to prevent him from having to talk about education. While taxpayers of the state’s five big-city school districts directly support those schools through city taxes, only one mayor, Michael Bloomberg of New York City, has direct control over schools. The others have only the power of the purse – hardly insignificant – and the bully pulpit as tools of influence. Brown employs neither.

Maybe Brown has a good reason for not being more involved in the schools. If so, as News reporter Mary Pasciak wrote Saturday, he ducked several opportunities to reveal them.

It could be the lack of direct influence that causes Brown to demur. That would certainly be understandable. If he starts defending taxpayers’ interests, taxpayers might also want to hold him accountable for improvement in a district that needs it the way a drowning man needs air.

But understandable isn’t the same as acceptable. While the city contributes only 8 percent of the district’s budget – about half of what Syracuse and Rochester contribute and less than one-fifth what Yonkers provides – that still amounts to more than $62 million. That’s more than petty cash, and city residents need municipal involvement in this issue.

The mayor can point to one initiative: a summer reading program that involves 1,000 of the city’s 33,000 students.

The main point, of course, is the education of Buffalo’s students, who have long been deprived of the “sound, basic education” to which the state constitution entitles them. That is mainly the task of the School Board, the superintendent and her principals and teachers. Still, Brown might profitably take an interest there.

More compelling is the role that education plays in improving the city economy. As long as Buffalo’s school system is under-performing, few families will want to move in and some will want to move out. A functioning school district – one that parents feel confident is giving their children the start they need to succeed in later years – is critical to attracting families and businesses, both of which pay city taxes.

Brown is not alone among mayors in maintaining a distance from the problems of education, but some of them are leading the way.

Syracuse Mayor Stephanie Miner interviewed the finalists for school superintendent during last year’s search. Two years ago Robert Duffy, then the mayor of Rochester and now the state’s lieutenant governor, unsuccessfully pushed for mayoral control of the city schools.

And Albany Mayor Jerry Jennings is blunt about the issue: “I don’t have time to run the schools,” he said in a video online, “but I do think that it’s important that any mayor in any city is part of what’s going on in the schools. I talk to mayors across the country, and their biggest challenge is, ‘OK, well, how do we maintain or get a higher graduation rate for our kids?’  ”

That’s what Buffalo residents have a right to expect from their leader. It’s something to consider during next year’s mayoral election.