Editor’s Note: This has since been retracted because we used incorrect data. Please read the correction for more.

 Earlier this year, San Diego Unified’s leaders warned parents that classroom sizes were about to spike.

They’d just laid off 1,500 educators — including about one in five teachers — as part of a plan to resolve an estimated $122 million budget shortfall.

Without concessions from the teachers union, district leaders said, the laid off educators would not return to classrooms this fall. Their classes would be consolidated and their students would end up getting less individual attention.

The teachers union eventually agreed to make concessions, a deal that will allow the laid-off teachers to return. Class sizes won’t increase.

But now, with the positions restored, it’s actually possible that classroom sizes will get smaller this fall. That’s because San Diego Unified expects enrollment to decline by about 1,400 students. The district will still employ the same number of teachers.

Whether class sizes get smaller depends on a few factors that aren’t yet set in stone. The district hasn’t finalized teacher assignments and its projected enrollment could be wrong.

Still, the possibility spurred me to take a historical look at teachers and student enrollment. Class sizes are often thrown around as a key metric of the district’s quality of instruction. They’re often used to pressure budget decisions like the union deal. I wanted to examine long-term trends to help gauge where we are now.

What I found: While the number of students and teachers has fallen in the past decade, they haven’t declined by the same degree. In 2011, the district actually had fewer students per teacher than most years in the previous decade.

That contrast represents a striking difference from how district and union officials often talk about the current state of San Diego Unified. They both argue the budget has been cut to the bone and no more teachers can afford to be cut.

The district has lost teachers. But it’s lost even more students.

To examine this trend in more detail, I’ve created three graphics below.

1. Student Enrollment

The graphic below shows student enrollment at district-run schools since 1998.

As we’ve previously explained, the growing popularity of charter schools is partially responsible for declining enrollment at San Diego Unified. The district lost about 16,600 students between 2001 and 2011. At the same time, charters gained about 7,500.

2. Number of Teachers

District leaders often lament charters during budget hearings, because fewer students attending their regular public schools means less money for the district. Millions of dollars each year is tied to student attendance. When fewer kids show up to class, less money is available to pay for things like teachers.

What’s often missing from the district’s hearings are statistics on the number of teachers that San Diego Unified has continued to employ despite declining enrollment. The graphic below illustrates the number of teachers, according to annual records from the state Department of Education.

(A quick note: One teacher doesn’t necessarily mean one person. The data represents the equivalent of one full-time teacher, which may include multiple part-time employees.)

3. The Big Picture

Two trends stand out by comparing the graphics above. First, the number of teachers continued to grow at San Diego Unified even after enrollment started to decline. Second, the number of teachers sometimes increased despite continued falling enrollment (i.e. 2006 and 2011).

It might help to look at the trend another way. The graphic below illustrates the number of students at San Diego Unified per teacher. Though San Diego Unified cut teachers in each of the five most recent years, the ratio remained relatively flat because enrollment also declined.

Between the peak of enrollment in 2001 and 2011, San Diego Unified lost about 14 percent of its students. In the same period, the district cut the equivalent of 659 teachers — a 7 percent decrease.

The graphics above address an interesting question that seems to get little public discussion. How many teachers does San Diego Unified need? The response — at least from district officials, union leaders and many parents — is often explained in vague terms like “more” or “as many as possible.”

The graphics above don’t answer the question, but I’m hoping our readers will weigh in after looking at the trends we’ve identified. Please share your thoughts in the comments section below or email me directly.

Keegan Kyle is a news reporter for Voice of San Diego. He writes about local government, creates infographics and handles the Fact Check Blog. What should he write about next?

Please contact him directly at keegan.kyle@voiceofsandiego.org or 619.550.5668. You can also find him on Twitter (@keegankyle) and Facebook.

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