Background: Many people find it difficult to make decisions about what to believe or do regarding “health actions” (things that they can do to care for their health or the health of others). To avoid being misled by unreliable information and to make good choices, people must be able to understand and apply some basic principles (concepts). The Informed Health Choices (IHC) secondary school resources are designed to help students learn and use nine of these concepts. This is a protocol for a prospective meta-analysis of three cluster-randomized trials in Kenya, Rwanda, and Uganda. Objective: To estimate the effect of using the IHC secondary school resources in addition to the standard curriculum compared to the standard curriculum in the context where the trial is conducted) on students’ ability to think critically about health actions. Methods: The participants are lower secondary school students (age 14-16) and their teachers. The intervention is a 2-3-day teacher training workshop, a teachers’ guide, and 10 40-minute lessons taught to the students during a single school term. The comparison is the standard curriculum in each country. The primary outcome measure is the Critical Thinking about Health (CTH) Test. The test is a measure of an individual’s ability to understand and apply the nine key critical thinking concepts included in the lessons. It includes two multiple-choice questions for each concept. The primary outcome is the proportion of students with a passing score on the test. Secondary outcomes include the average score on the test, the proportion of students with a score that indicates mastery of the nine concepts, retention of what the students learned after one year, self-efficacy, intended behaviours, performance on standard, end-of-term examinations, and teachers’ ability to understand and apply the nine concepts measured using the CTH Test. Overall effects will be estimated using inverse variance methods. We will use mixed effects models with individual student data to estimate variation in effects for the primary and first two secondary outcomes in relation to three potential effect modifiers: use of a projector version compared to a blackboard version of the lessons, class size, and student performance on end-of-term examinations prior to the intervention. Strengths and limitations: Strengths of this meta-analysis are that it is prospective, allowing for collaboration on the design of the trials and certainty that all eligible trials have been included. A limitation is that the review authors are both developing and evaluating the intervention, although there are efforts to minimise bias.