This study investigates K–12 educators’ preferences for lesson plans created by humans versus AI models. Surveying math teachers across grade levels, the research compares components like warm-ups, main tasks, and cool-downs. While human-authored plans are generally favored—especially in elementary grades—AI-generated lessons perform well in structured tasks like cool-downs, particularly in high school. Teachers value the adaptability of AI but rely on human expertise for differentiation and student discourse. The findings support a collaborative approach where GenAI serves as a planning assistant, not a replacement.