Existing curriculum learning methods for reasoning reinforcement learning often treat problem difficulty as a static property of the problem. We argue that difficulty is instead policy-dependent: problems beyond the current policy provide sparse learning signals, while problems already solved by greedy decoding may still yield informative stochastic trajectories during RL. We propose PAD-Curriculum, a policy-adaptive curriculum framework for GRPO that estimates the student’s evolving solvable frontier from student-generated trajectories. For currently solved problems, PAD-Curriculum ranks examples by a normalized Scorer-to-Student KL discrepancy computed against a frozen stronger scorer; unsolved problems are deferred and periodically re-evaluated as the policy improves. Experiments on GSM8K, MATH, and NuminaMath-CoT with Llama-3.1 and Qwen3 models show consistent gains over standard GRPO and curriculum/distillation baselines, with particularly strong improvements on challenging mathematical reasoning benchmarks. Analyses further show that adaptive discrepancy estimation is more effective than static scorer-based difficulty.