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Skill-Aware Data Selection and Fine-Tuning for Data-Efficient Reasoning Distillation

Paper · 2026 · Lechen Zhang, Yunxiang Zhang, Wei Hu et al.

Summary

Distilling reasoning from large models such as DeepSeek-R1 into smaller LLMs usually relies on large SFT datasets in which every example counts the same. That approach ignores both which skills a problem requires and what the student model already knows. The authors propose a skill-centric distillation framework for math reasoning built on a hierarchical skill tree taken from Instruct-SkillMix. First, Qwen2.5-32B-Instruct labels each problem in a 100K OpenMathReasoning pool by walking the tree from the root down to the relevant leaf skills. Second, the student is evaluated on the pool, and training examples are drawn with probability inversely tied to the student's accuracy on each skill. Third, the full skill chain is inserted before each solution, so the model learns to name the skills it needs before it starts reasoning. With only 1K selected examples, this beats random selection on Qwen3-4B and Qwen3-8B. The gains concentrate on weaker skills, which makes per-skill performance more even. The work shows that careful, model-adaptive data selection can count for more than data volume.

Key points

  • Gains over random 1K SFT: +1.6 Avg@8 on Qwen3-4B (68.4 vs. 66.8) and +1.4 on Qwen3-8B (69.5 vs. 68.1). Evaluation used five benchmarks: AMC23, AIME2024, AIME2025, MATH L5 and OlympiadBench.
  • Full-corpus fine-tuning hurts: training on all 100K examples drops accuracy below the base model (58.1 vs. 67.1 for Qwen3-4B).
  • Sampling ablation: an accuracy exponent of T = 1.0 works well, and more aggressive settings saturate.
  • Skill-chain ablation: the full chain (72.9) beats root-only (72.2) and leaf-only (72.7) skill labels.
  • Generalization (Appendix C): the method also works with the EvalTree taxonomy and with R1-Distill-Llama-8B. It outperforms the LIMO, s1, Light-R1 and Select2Reason baselines. Code and data are released at github.com/orange0629/skill-data-selection.

Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.

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Cite

Cite as Lechen Zhang, Yunxiang Zhang, Wei Hu and Lu Wang. 2026. Skill-Aware Data Selection and Fine-Tuning for Data-Efficient Reasoning Distillation. Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers).

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.18653/v1/2026.acl-short.49

@inproceedings{zhang2026skill,
  title = {{Skill-Aware Data Selection and Fine-Tuning for Data-Efficient Reasoning Distillation}},
  author = {Lechen Zhang, Yunxiang Zhang, Wei Hu and Lu Wang},
  booktitle = {Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers)},
  year = {2026},
  doi = {10.18653/v1/2026.acl-short.49},
  url = {https://doi.org/10.18653/v1/2026.acl-short.49}
}

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