Tuesday, December 01, 2015


Cohorts and Critical Mass

This one is best expressed as a word problem.  And no, it doesn’t involve trains heading in opposite directions.

You can’t afford consistently to run classes below fifteen students.  You build a tightly-constructed two-year program on a “cohort” model: in other words, on the assumption that students will move through as a bloc.  How many students do you need at the outset to make the program viable?

  1. it’s only money
  2. 15
  3. 25
  4. 30+

The correct answer depends on institutional context.  In an amply-funded institution, or with a really killer grant behind it, “a” could be right.  In a residential college full of high achievers who attend full-time and have an on-time graduation rate over 90, b might be correct.  In a community college, though, even c would be optimistic.  I’d go with d.


Voluntary, informal cohorts fly apart quickly.  

Let’s say you get lucky and 30 students sign up for the first attempt.  Congratulations!  But eight of them need developmental classes, and another five bring some odd mix of transfer credits.  Now your first-semester classes range from 17 to 30.  

Assume that three students fail or drop out from the primary cohort.  (That’s pretty optimistic.)  Assume that another two drop out from the developmental classes.  At the second semester, you’ve got the “catchup” first semester classes running at six each, with the second-semester classes running at 14 to maybe 27, if you’re lucky.  (With transfer credits, the max is probably closer to 25.)  

Repeat, then repeat again.  By the end, you’ve got class sizes you can’t support, but you’re locked in because students need them to graduate.  Between the classes you planned to run and the catchup classes for the ones who either started or fell behind, you’re swimming in single digits.  And even if you closed the door behind the first cohort, you have an ethical obligation to the first cohort to give it a reasonable shot to finish.

Yes, there are exceptions.  Some employer-based programs hold together much better than that, because there are immediate economic rewards and penalties.  Selective programs also do better, because they’ve screened out the still-developmental and other high-risk groups at the outset.  Programs with captive populations -- high schools or prisons -- prevent attrition by preventing leaving.  But for programs built to take all comers and to last two years or more, this is a broadly accurate picture.

In the absence of either a grant or some other third-party payer (i.e. an employer), it’s easy for a program like this to start circling the drain.  And that’s assuming a relatively healthy sized starting group.  Start with 20 instead of 30, and things get uglier faster.

The folks who want community colleges to respond immediately when the economic winds shift often don’t understand this.  Absent some sort of funding cushion, the nightmare scenario is that you start with 15 to 20.  Turning away that many looks heartless and/or stupid; starting with that many virtually guarantees sustained losses.  

If we want community colleges to be more entrepreneurial and to take more risks like these, they need the funding to do it.  In the private sector, that would be so obvious as to seem tautological: investment requires capital.  But in the public sector, it’s considered suspect.  It shouldn’t be.  Here, too, investment requires capital.  We just don’t call it that.

If we could afford answer A, we could do nearly anything.  Even answer B would allow far more responsiveness to local conditions than we can manage now.  As long as we’re stuck with “maybe C but probably D,” well, some needs will go unmet.  I’d like to change the direction of that train.

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