The purpose of this study is to investigate the effectiveness of two instruction methods for teaching polysemous English prepositions ("at, in, on") and to explore learners' perception on learning tools used in the instruction when learning polysemous words. The first study investigated the effectiveness of schema-based instruction (SBI), which is a form of instruction based on the insights of cognitive linguistics (CL) and is a way of teaching, which provides learners with the schematic core meaning. Whereas, translation-based instruction (TBI) is one of the conventional ways of teaching prepositions as polysemous words, which offers learners a list of several meanings of each preposition. Two tests, as pre- and post-tests were carried out to examine the effectiveness of the instruction. A second study explored how leaners perceived the learning tools in each instruction method. The methods consist of the core schema and translations in dictionary, which were analyzed with the motivation to be able to conduct more effective instruction on polysemous words in the classroom. For this study, data was collected by a questionnaire and analyzed qualitatively to extract constructs that learners have on both instructions. Based on the results of these two studies, this paper argues that the core-schema approach to teaching English propositions is more effective than the conventional approach. Furthermore, the core schema approach is practical to administer to learners; however, it was discovered that learners perceived both benefits and disadvantages in the two instruction methods and suggested the necessity of separate-use depending on the learning situation.