When Greg Sumlin looks at the incoming kindergarten class at East Elementary School in Littleton, he sees a group of English learners who need immediate, intensive instruction — in small classes where teachers can give them individual attention.

Then he looks at this year’s first-graders, calculates his staffing and crunches the numbers: although these kids also have high needs, three classrooms of 16 or 17 will have to be shoe-horned into two second-grade classes of 23.

It’s a vexing academic sudoku that principals tackle — and teachers must adapt to — as schools try to line up budgets, staff and attendance projections in pursuit of an elusive educational sweet spot: effective class size.

“We’re still talking about it and will be all the way to the start of the school year,” said Sumlin, whose school was recognized by the state last year for its progress with a largely at-risk population. “It’s a problem-solving process we need to get through.”

Class size generally is determined on a building-by-building basis. But the trend of districts’ student-to-teacher ratios in Colorado, as calculated by the Colorado Department of Education, has been upward as budget cuts have taken a toll over the past five years.

Though district-wide averages may vary by only one or two students from year to year, individual classes can fluctuate significantly as principals weigh tough decisions on where to deploy resources.

Class size remains part of the debate over competing priorities at a time of fiscal constraint, increasing accountability and the ever-shifting shape of reform. Some reform advocates discount the impact of class size on student achievement in favor of focusing on what they consider a higher priority: teacher effectiveness.

“The combination of the recession with this push for quality teachers, the nexus of the two, is why we’re seeing this move away from class size,” said Kristin Klopfenstein, who heads the Education Innovation Institute at the University of Northern Colorado.

Generally, research into the effect of class size on achievement has found that it can have significant impact in kindergarten to second grade, though findings are mixed after that. But large increases in class size suggest certain intuitive results — challenges in classroom management, less individual attention, a reluctance to assign homework — that could affect student performance.

On the other hand, the “fashionable” research, as Klopfenstein calls it, zeroes in on teacher effectiveness as a more cost-effective remedy than hiring more teachers to reduce class size.

“If a teacher doesn’t do anything differently, teaches the same way big or small, then I don’t think less is better,” Klopfenstein said. “It’s just more expensive. If they’re really an effective teacher, then what they’re doing with 18 kids could probably be done just as effectively with 27.”

That’s a sentiment repeated among high-level administrators presented with the issue of class size. They almost immediately shift the conversation to effective teachers.

“If my children could have a teacher who was not as great in a class of 22, or a phenomenal teacher with 28 or 30, and you gave me that choice as a parent, it’s very clear I’d choose the latter,” said Tom Boasberg, superintendent of Denver Public Schools.

U.S. Secretary of Education Arne Duncan not only emphasizes teacher effectiveness, but takes it a step further. He proposes not just putting more kids with the best teachers, but also paying those teachers more.

“So if you have a good teacher with higher class size, and they’re compensated more, the district saves money and you have a higher percentage of kids with strong teachers if you do it systemically,” Duncan said.

But some experts maintain that class size not only is a proven indicator of improved achievement, but a cost-effective one as well.

Alex Molnar, a research professor for the National Education Policy Center at the University of Colorado at Boulder, recites the talking points dismissing the impact of smaller classes as opposed to more effective teachers and then pauses.

He punctuates the litany with a single, emphatic expletive.

Molnar, who headed a major study of class size in Milwaukee schools, contends that the research — particularly at the younger grades — is formidable in favor of smaller numbers. The initial investment in more teachers, he says, ultimately saves money by producing gains that carry through to college.

He adds that smaller class size remains a major factor in attracting quality teachers at any grade level, particularly in hard-to-staff schools trying to close the socioeconomic “achievement gap.”

“Parents want it, teachers want it, schools use it as a selling point,” Molnar said. “And yet, those intuitive perceptions about the advantages of smaller classes seem to be trumped, in many cases, by the topic of effective teachers and conflicting data.”

Molnar also casts the discussion in larger political terms — which is to say, he sees elements of the reform movement ill-advisedly shoving public education toward privatization. Making a case for larger classes means fewer teachers and lower expense.

“The principal reforms promoted in education policy right now are not reforms associated with education — the reforms are about money,” he says. “Class-size reduction can’t be allowed as a policy matter because it directly reduces the trajectory that’s being attempted. It threatens the possibility of making a profit.”

The class-size discussion eventually veers in yet another direction — its long-term effect on teachers.

At Mountain Range High School in the Adams 12 district, Brandi Potestio teaches five English classes heavy on writing. Three years ago, she averaged about 25 students per class. That number now hovers around 33.

The difference, multiplied by five, comes to roughly another class-and-a-half of pupils based on her former averages. For her, class size isn’t just a factor. It’s the biggest factor — especially in a subject like English that often requires complex student evaluation.

“Grading is insane,” Potestio said. “It’s always time-consuming, but when you increase class size, it’s overwhelming. I can see why some teachers don’t assign a lot. I wish I could (assign less), but it’s not in my DNA.”

The result can be burnout, if the current trend continues.

“They’ll lose good teachers,” Potestio said. “If you’re a good teacher, you know that this is not possible forever, unless you want to have zero life.”

Smaller class size has a proven track record — but only when a teacher effectively uses it to individualize instruction, offers Diana Sirko, deputy commissioner at the Colorado Department of Education and a former district superintendent, principal and math teacher.

But, she adds, raw numbers do matter: From kindergarten through third grade, class size of no more than 20 makes sense; 25 represents a reasonable middle ground for most other grades — though context and common sense should rule over any rigid formula.

“I think when you get above 30 students,” she said, “there’s a law of diminishing returns in terms of teachers’ ability to tailor instruction around individual needs of students. It can be done, but that doesn’t mean it’s the best conditions for success.”

Van Schoales, head of the reform group A+ Denver, takes the issue in an entirely different direction. He says that using class size to frame the discussion of how schools apportion resources isn’t particularly helpful in the first place.

“Class size forces you to basically fit in the current paradigm of how schools are organized,” Schoales said. “If those things were working well, and if there was a direct relationship to student achievement, it might be a good way to talk about this stuff. But there isn’t. It’s much more helpful to talk about an amount of money and work backwards to see the most effective way to pull together resources.”

Meanwhile, parents like Marykay Cicio keep tabs on class size amid painful budget cuts while education reformers repeat the mantra of providing every child a highly effective teacher.

Cicio, a parent and part-time tutor at Boulder’s Creekside Elementary, said she’s all for skilled teachers. But she can do the math: the bigger the class, the less attention her child gets.

“We have all these goals and aspirations to attract the best and brightest into every classroom. Great goal,” Cicio said. “But what happens to kids right here, right now, suffering consequences of budget cuts?”

Kevin Simpson: 303-954-1739 or ksimpson@denverpost.com