Open AccessThis paper examined the efficiency of using complex situations in teaching Science and Elementary Technology in 20 primary schools, 38 classes ( only fourth years), located in Huye district in Rwanda. The sample was divided into four groups: 9 classes practiced the “teaching situations”, 9 dealt with “integration situations”, 9 mixed “teaching and integration situations” and 11 classes made a “reference group” that did not use any of those approaches. One pre-test and three post-tests have been done by learners from those classes during the 2012 school year. Every test had a “resource” test and a “situation” test with a similar level of difficulties. The analysis indicated progressive increase of marks, especially, for the classes which practiced the “integration situations”. The findings showed a priority of starting with the “integration situations” for the development of the learner’s autonomy and of a cognitive development.