Assessing teacher-student interactions in the classroom is critical, but most research has relied on short observation periods due to the infeasibility of longer sessions. Our study assessed and quantified the emotional tone (i.e., teacher sentiment) of classroom teachers' language patterns throughout the school day using transcriptions of 149 full-day videos to understand the consistency of findings with prior research, relations to discipline referrals, and sensitivity to professional development (PD). Using natural language processing, we found emotional tone varied by grade levels taught and time of day. Teachers of younger grades used more positive language, and more positive language was used at the start of the school day for all grade levels. We also found teacher emotional tone was significantly related to their overall use of discipline referrals. Furthermore, emotional tone detected effects of a professional learning equity-focused intervention. Across conditions, more positive emotional tone was associated with fewer discipline referrals throughout the year. However, teachers in the intervention group demonstrated even more positive emotional tone and lower use of discipline referrals. The results are discussed in terms of classroom observations technology and strategies to improve student outcomes. [This paper was published in "Journal of Positive Behavior Interventions" v27 n4 2025.]