How Uncertain Is the Grade? A Benchmark of Uncertainty Metrics for LLM-Based Automatic Assessment. - Hang Li 007; Kaiqi Yang 001; Xianxuan Long; Fedor Filippov; Yucheng Chu; Yasemin Copur-Gencturk; Peng He; Cory Miller; Namsoo Shin; Joseph Krajcik; Hui Liu 031; Jiliang Tang (CoRR, 2026)