This paper reports the qualitative analysis of science teachers' pedagogical reflections while attending institutes focused on the "Next Generation Science Standards" (NGSS). The researchers collected reflection slips from 165 science teachers (K-12) across 14 different NGSS institutes. To analyze the data, researchers classified teachers' written thoughts using the six subscales included in the Science Teachers' Pedagogical Discontentment (STPD) scale. Doing so revealed that teachers often grounded their reflections in three-dimensional instruction. Looking closely at each dimension, teachers reflected on science and engineering practices (SEPs) more often than the dimensions of disciplinary core ideas (DCIs) and crosscutting concepts (CCs). However, these latter dimensions incited discontentment more than SEPs. Teacher thinking was not confined to classroom practice. A portion of teacher reflections cited the planning process as cognitively demanding, thus, supporting a broader definition of pedagogical discontentment. When considering how teachers realized a mismatch in practice and/or planning, institute discussions incited discontentment to a higher degree than doing an activity or watching a reform-based strategy. These research findings have implications for how future professional developments should be structured to incite dissatisfaction and align teacher thinking with the NGSS vision.