The importance of tooth brushing in oral health is evident, since doing it incorrectly can lead to diseases such as cavities and gingivitis, especially in the school population. The objective of this study was to analyze the relationship between knowledge, attitudes and practices regarding tooth brushing and bacterial plaque levels in 12-year-old schoolchildren from the Trujillo-Peru district, before and after implementing an educational strategy. A descriptive and correlational study was carried out with the participation of 247 schoolchildren of both genders. A survey on tooth brushing was administered, and levels of bacterial plaque were measured using the Green and Vermillon Oral Hygiene Index before and after the educational strategy on brushing technique. The results revealed that knowledge about tooth brushing in schoolchildren was poor before the educational strategy, improving significantly after implementing it. Attitudes and practices also showed substantial improvements, going from low levels to regular and good. It is concluded that the educational strategy managed to improve the knowledge, attitudes and practices related to tooth brushing in schoolchildren, evidencing a positive impact on the reduction of dental plaque, improving the oral health of the participants.