Train-the-Trainer Models for Vietnamese K-12 Informatics Curriculum Rollout: A Literature Synthesis

Vietnam's General Education Curriculum 2018 (CT 2018) makes informatics (Tin học) a compulsory subject from grade 3 onward, generating a curriculum-rollout problem of national scale: tens of thousands of in-service teachers must acquire content rigor and pedagogical content knowledge in a subject many of them did not train for, against a fixed cascade structure (central — provincial — school) inherited from the bòi dưõng thưòng xuyên (continuous professional development) framework codified in MOET Circular 17/2019. This paper synthesises the train-the-trainer (T-T-T) literature relevant to that problem. Four named models are compared: single-tier cascade (M1, the dominant inherited form), hub-and-spoke (M2, exemplified by England's Computing-at-School Master Teacher network), professional learning community (M3, exemplified by the Exploring Computer Science summer-institute-plus-monthlyPLC design), and online cohort with optional coaching (M4, exemplified by the Australian CSER MOOC). Each model is evaluated against five criteria — cascade-fidelity preservation, time and cost per trained teacher, content-rigor preservation, retention after one year, and alignment with the existing MOET cascade. The empirical record is consistent on three points: single-tier cascade alone produces fidelity loss and message distortion at each hop; one-shot workshops without follow-up coaching produce transfer rates of approximately five to ten percent against the eighty-plus percent transfer observed under sustained coaching (Joyce and Showers 2002); and contentfocused, collaborative, sustained-duration PD with model-andcoach features (Darling-Hammond, Hyler and Gardner 2017) dominates the comparative evidence across PD types. The recommended model for the Vietnamese rollout is a hybrid: a contentfocused central core institute (M3 in design, M1 in delivery to lead teachers), a regional hub layer that supplies coaching capacity (M2), school-cluster professional learning communities for sustained practice (M3), and an online refresh layer for reach beyond the chuyên-school cluster (M4). The hybrid is calibrated for FS2P, PP, and CPP series rollout; CPP additionally requires content-rigor preservation safeguards distinct from FS2P. Three open questions are flagged: whether the hybrid's coachingcapacity layer can be staffed at scale, how content rigor is preserved across cascade hops for the competitive-programming track, and whether MOET regulation will accept the hybrid's longer time-to-trained-teacher in exchange for higher retention.