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A quick thread about a really brilliant new paper on instructional coaching in initial teacher training by Cohen, Wong, Krishnamachari & Berlin... 
Although there has been progress in our understanding of effective in-service (continuing) professional development for teachers, we still know very little about effective pre-service (initial) teacher training. This paper provides powerful new evidence on the latter...
The authors use an experiment to test how quickly trainee teachers develop certain new skills under three conditions:
1) practice, personal reflection, practice
2) practice, instructional coaching, practice
3) practice with prompts, instructional coaching, practice
1) practice, personal reflection, practice
2) practice, instructional coaching, practice
3) practice with prompts, instructional coaching, practice
Trainees are coached on a specific skill: redirecting disruptive behaviour in a way that is: timely, specific, succinct and calm. The coaching protocol uses open-ended directed questions, asking trainees to give examples of applying the methods well & not so well ('non-examples')
In the 'practice with prompts' condition teachers also get a 'bug in the ear' (BIE) device that gives them concise instructions during the early stages of practice, rather than having to wait until after the practice session.
The outcome measures are observation scores given by observers, who are looking to see whether the trainees are able to use the techniques effectively. The raters are trained, blind to whether the trainees are in conditions 1), 2), or 3), and their ratings show high reliability.
Results are similar across all outcomes (2 shown below). Trainees with instructional coaching and prompts (3) showed the fastest gains in skill, but trainees with just instructional coaching (2) showed similar gains over a longer period. (NB: lower is 'better' on the left graph)
Another common finding is that practice with reflection (but no feedback in the form of instructional coaching) leads to small/zero gains, across all the outcomes measured. Practice followed by personal reflection by trainees is not enough to embed new teaching skills!
A distinctive feature of this training: the practice takes place in a virtual environment, which allows 1) the practice to be carefully controlled/varied 2) the extraneous load on the trainee to be minimised and 3) the trainee can repeat the same exercise, following feedback
There is plenty more that is interesting about this paper - not least that it provides yet more evidence for the power of instructional coaching.
I recommend you check it out for yourself: https://journals.sagepub.com/doi/10.3102/0162373720906217
I recommend you check it out for yourself: https://journals.sagepub.com/doi/10.3102/0162373720906217