This study investigates community sentiments and opinions regarding the use of ChatGPT in education within online user forums. Large Language Model (LLM)-based sentiment analysis was conducted on the posts and comments submitted to Teachers Subreddit, an online community for educators. The analysis revealed that the members of Teachers Subreddit expressed more negative sentiments towards the use of ChatGPT in education compared to those who shared their opinions on X (formerly known as Twitter). Additionally, LLM-based topic modeling was performed on the positive and negative opinions identified during the sentiment analysis phase. Seven positive topics emerged: (1) ChatGPT as a content generation tool, (2) enhanced student engagement, (3) embracing changes, (4) need for effective professional development, (5) educational reform, (6) plagiarism-detection software, and (7) utilizing ChatGPT in writing classes. Seven negative topics were also identified: (1) challenges in education, (2) increase in plagiarism, (3) ineffective professional development, (4) academic dishonesty, (5) negative effects on the workforce, (6) curriculum relevance and meaning of education, and (7) lack of emphasis on critical/higher-order thinking skills.