What is a stretch assignment, and should you take one?
A piece of work deliberately beyond your current demonstrated capability, given as a development opportunity — and the evidence that it is how people actually develop is stronger than the evidence for most formal training.
The underlying model. The frequently cited 70-20-10 framing holds that development comes largely from challenging experience, partly from relationships and feedback, and only a small proportion from formal training. The specific proportions are not well evidenced and are best treated as a rough heuristic — but the direction is well supported: people develop by doing difficult things with support, not by attending courses.
What makes an assignment genuinely developmental: unfamiliar responsibilities; a higher stake than usual; working across boundaries with people you do not normally deal with; ambiguity, with no established method; and visibility, so the work is seen by people who make decisions about you.
Why they matter for progression. Promotion decisions rest on evidence of having operated at the next level, and you cannot produce that evidence without having been given the chance. This creates a circularity that stretch assignments break.
The equity problem, which is well documented. Research on work allocation has repeatedly found that high-visibility, career-advancing work is distributed unevenly, while non-promotable tasks — organising, note-taking, committee administration, pastoral support — fall disproportionately on women and on under-represented groups. Because these tasks are valued in the moment and not at promotion, the effect compounds over a career.
Worse, people who decline such tasks are judged more harshly for declining than others are, which makes refusal costly.
What to consider before accepting:
Is there support? A stretch without sponsorship, resources or access is a set-up rather than an opportunity.
What happens if it goes badly? Development requires permission to fail, and if failure would be career-limiting it is not a development assignment.
Is it visible, or invisible work labelled as development?
What are you giving up, since capacity is finite.
Is it additional or instead of? Stretch work added to a full workload is not an opportunity.
How to ask for one: identify the level you want to demonstrate, propose specific work, and name the support you need.