This thesis presents the result of descriptive study of Problem-Based Learning strategies found in the character of Sherlock Holmes, the main character of novels and short stories by Sir Arthur Conan Doyle.
In obtaining data, the researcher collected various quotations throughout the novels and short stories.
After analyzing the data, there were found several kinds of code switching in the classroom such as inter-sentential switching, intra-sentential switching and tag switching. Intra-sentential switching was the most-performed type in the code switching use in the classroom. In performing code switching, both the teacher and the students switch between English language, Bahasa Indonesia and sometimes Javanese language as well. In analyzing the code switching factors, the researcher found 7 factors of why code switching was used in the classroom, they are quotations, addressee specification, repetition, interjection, message qualification, personalization and objectivization as well as facility of expression. However, code switching phenomenon is common in EFL classroom even in international standard school. therefore, solutions were offered for the teachers to eliminate the use of code switching. Suggestions have also been investigated to deal with the problems.
Finally, this study is expected to be beneficial to English Language Teacher, Students, and future researcher who expects to conduct the similar study. Since Interanational Standard School has been terminated, this study will give descriptionsof the language use in international standard school. This makes sense since this study will give contributions to the development of English Language use in the classroom in the future.

Keywords: Problem-Based Learning, Problem Solving, EFL Classroom,