Rubric-Aware Multi-Expert Online Policy Distillation for Chinese Elementary School Essay Writing

Wei Tian, Yuhao Zhou, Xiayu Sun, Yadong Zhang, Hao Zhou, Shu Liu, Man Lan


Abstract
Chinese elementary-school writing is rubric-driven. We study it as a teacher-facing instructional support task: given a classroom prompt and requirements, generate a teacher-reviewable example matching the target genre, rubric, length, and age-appropriate register. Directly prompted frontier LLMs often mis-route genres or adopt an adult register.

We present **RA-MOPD**, a four-stage pipeline that post-trains a 4B model into a unified essay writer across four genres and eight rubric dimensions. Its core stage augments on-policy reverse-KL distillation with *Rubric-Weighted KL*, which up-weights rubric-critical tokens via reward-model attribution, and *Cross-Genre Mixing*, a parameter-free expert blend guided by an empirical transfer prior.

On a new 6,000-essay benchmark with eight reward models (QWK = 0.864), RA-MOPD reaches 4.21/5.00 and 97.8% routing—within 0.09 of GPT-5.3 3-shot (p < 0.01). No statistically significant difference is detected relative to a 4×-cost four-expert logit-averaging baseline (Δ = +0.03, p = 0.18).

A GPT-4.1 judge, BERTScore, a 1,200-essay teacher study (62.8% preference), and register analysis provide converging evidence beyond RM metrics. GPT-5.5 holistic evaluation further supports the component-level gains, which remain stable on Qwen3-1.7B without model-specific retuning.

Code and data: [https://github.com/TW-NLP/MOPD](https://github.com/TW-NLP/MOPD)
Anthology ID:
2026.emnlp-main.1115
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
25543–25565
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1115/
DOI:
Bibkey:
Cite (ACL):
Wei Tian, Yuhao Zhou, Xiayu Sun, Yadong Zhang, Hao Zhou, Shu Liu, and Man Lan. 2026. Rubric-Aware Multi-Expert Online Policy Distillation for Chinese Elementary School Essay Writing. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 25543–25565, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Rubric-Aware Multi-Expert Online Policy Distillation for Chinese Elementary School Essay Writing (Tian et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1115.pdf