Aims and Objectives:To assess the early effect of oral health education on oral health knowledge of primary and intermediate school students of private schools by utilizing pre/post questionnaires data from oral health educational projects in Riyadh city, Saudi Arabia. Second, to examine topic-specific knowledge differences between genders, nationalities, and educational levels of the students.Materials and Methods:Cross-sectional oral health educational data of private school students (n = 1279) in primary and intermediate levels were extracted from the King Salman Centre for Children's Health (KSCCH) projects undertaken by Riyadh Colleges of Dentistry and Pharmacy. Student's pre- and post-test data were analyzed for changes in oral health knowledge. Overall knowledge score and topic-specific knowledge scores were calculated and the differences between gender, nationality, and educational level were examined using Mann–Whitney U-test. Pre/post change in the oral health knowledge was evaluated by Wilcoxon's sign rank test.Results:Immediately, after oral health educational session high knowledge score category showed an increase of 25.6%, medium and low knowledge score categories showed −3.2% and −22.3% decrease, and this change was statistically significant (P < 0.001). Comparison of correct responses between pre- and post-test showed statistically significant (P < 0.05) increase in all the questions except for the timing of tooth brushing. Females, non-Saudi nationals and students in primary level of education showed significantly high mean knowledge (P < 0.001) at posttest assessment.Conclusion:Primary and intermediate private school student's overall, and topic-specific oral health knowledge improved immediately after educational intervention provided by KSCCH. High knowledge gain was observed among female non-Saudi primary school students.