This study is conducted in a classroom action research to improve the students' achievement in writing English sentences in Present Perfect Tense in Structure 1 lessons. The subject consisted of 20 Semester II students who took Structure I lessons in English Education

This study is conducted in a classroom action research to improve the students' achievement in writing English sentences in Present Perfect Tense in Structure 1 lessons. The subject consisted of 20 Semester II students who took Structure I lessons in English Education Department of Palangka Raya University, Central Kalimantan, Indonesia. The data were taken from the results of pre test and post test after the action was done. The results show that in cycle 1, in which the explanations were fully in English, only 40% of the students got a good achievement; 5-7 out of 20 test items were correct. After cycle 2 was done using L1 interchangeably with English in the explanations, the students' achievement of writing English sentences in Present Perfect Tense increased to 75%, in which 15-18 out 20 test items were correct. Key words: L1, L2, EFLWhy should teachers use L1 in EFL classes? As stated by Carless (2008), L1 has potentially both positive and negative consequences. It may serve social and cognitive functions. Socially it serves to give instructions and rules, to establish attention, or to foster discipline, and to support classroom management, while cognitively it facilitates the students' understanding. He claimed that students working in group do not necessarily speak English all the time; therefore, L1 also occurs in the discussions since the students are linguistically incapable of activating English words and meanings.In the field of foreign language teaching especially English, various other professionals also agreed with the above statement that L1 has a necessary and facilitating role in L2 classrooms. For example, Auerbach (1999) pointed out that to start the classroom interactions using L1 provided a sense of security and validated the learner's live experiences. Pillay and Hwa (1997) even felt the disempowerment of monolingual English classes in EFL teaching in Malaysia, and Melayu language (L1) was also used instead of only English. They showed that in rural 171

This study is conducted in a classroom action research to improve the students' achievement in writing English sentences in Present Perfect Tense in Structure 1 lessons. The subject consisted of 20 Semester II students who took Structure I lessons in English Education Department of Palangka Raya University, Central Kalimantan, Indonesia. The data were taken from the results of pre test and post test after the action was done. The results show that in cycle 1, in which the explanations were fully in English, only 40% of the students got a good achievement; 5-7 out of 20 test items were correct. After cycle 2 was done using L1 interchangeably with English in the explanations, the students' achievement of writing English sentences in Present Perfect Tense increased to 75%, in which 15-18 out 20 test items were correct. Key words: L1, L2, EFLWhy should teachers use L1 in EFL classes? As stated by Carless (2008), L1 has potentially both positive and negative consequences. It may serve social and cognitive functions. Socially it serves to give instructions and rules, to establish attention, or to foster discipline, and to support classroom management, while cognitively it facilitates the students' understanding. He claimed that students working in group do not necessarily speak English all the time; therefore, L1 also occurs in the discussions since the students are linguistically incapable of activating English words and meanings.In the field of foreign language teaching especially English, various other professionals also agreed with the above statement that L1 has a necessary and facilitating role in L2 classrooms. For example, Auerbach (1999) pointed out that to start the classroom interactions using L1 provided a sense of security and validated the learner's live experiences. Pillay and Hwa (1997) even felt the disempowerment of monolingual English classes in EFL teaching in Malaysia, and Melayu language (L1) was also used instead of only English. They showed that in rural 171

Abstract-Appropriate use of English tenses and conventions is a must for students who write their thesis in English. It is imperative whether they are aware of the appropriateness to translate their research activities into a written form that conform to the expectations of scientific and academic community. A survey was conducted to 65 out of a population of 124 students of the English Education Study Program of Universitas Palangka Raya who were writing the draft of their research report. The survey was done to obtain data on the use of English tenses and conventions in the Introduction part of their thesis research report writing. The results showed that the inappropriateness of the use of English tenses and conventions occurred due to the lack of understanding on the appropriate use of the English tenses and conventions in the Introduction Part. They used incorrect tenses in stating the arguments and in quoting previous research results. They did not provide a clear setting to move from the general area toward more specific topic of the research. They could not differentiate report-oriented style from research-oriented style in communicating the information about their research.