Don't Overload Your Juniors
I was on a team that put junior developers into the on-call rotation earlier than we should have. The reasoning made sense on paper - they needed to learn the system, and the senior engineers were stretched thin. In practice, the juniors almost always needed to escalate to someone more senior. So a junior's regular work suffered because they were on call, a senior's work got interrupted by the escalation, and incidents took longer to resolve because they went through an extra hop.
I've seen the same pattern outside of tech. Junior staff whose primary job is to support senior employees start getting assigned the senior employees' actual work - not as stretch assignments with mentorship, but as regular workload. The juniors end up buried, the senior employees lose the support they depend on, and the reassigned work gets done at a junior level.
In both cases, the intent is usually reasonable. The seniors are overloaded, the juniors seem capable, and someone up the chain decides to redistribute. But the second-order effects are where it falls apart. The juniors' core work - the work they were hired and are ready to do - falls behind. The quality of the reassigned work drops. Some of them are overwhelmed, not learning, and eventually they leave. And the pipeline breaks, because nobody grows well under that kind of pressure.
The reason it keeps happening is that it looks like the right call in the moment. The seniors are overloaded, the juniors are available, and the work needs to get done. The juniors usually don't push back, because they're eager and want to prove they can handle it. And the junior's actual work - support, prep, coordination - is often invisible enough that nobody notices when it stops getting done.
But being able to handle a task with guidance doesn't mean you're ready to own the responsibility full-time. Management sees a capable junior and concludes they can take on senior work. What actually happens is the junior gets the work without the experience or support to do it well, and the senior loses the support they were depending on to do theirs.
If you think junior staff are ready for more responsibility, lean them into it gradually. Assign one or two projects for the year, not ten. If they handle those well alongside their existing workload and seem ready for more, add more. But their core work has to stay covered the whole time - the moment it starts slipping, you've gone too far too fast.
In my experience, protecting scope is management's job - not just for juniors, but for everyone who reports to them. When you overload your juniors without guarding their core responsibilities, it doesn't just hamper them. It hampers everyone who depends on their work. If your juniors are spending more time on senior work than on their actual role, that's a staffing problem, not a development opportunity.