This research aims to determine whether the use of WhatsApp social media during the Covid19 pandemic has an effect on teacher performance at UPT SPF SD Negeri 101877 Tanjung Morawa. The research method is a correlational research method. The subjects of this study were teachers at UPT SPF SD Negeri 101877 Tanjung Morawa in 2020/2021. The research sample was 20 teachers using the population research method. Data from this survey was collected through a questionnaire. The questionnaire used was tested for validity and reliability. While the data analysis method used is product moment correlation. Based on the calculation results obtained r count of 9.566, and these results are compared with r table at a significance level of 5% (2.086). This means that the use of WhatsApp social media affects the performance of teachers UPT SPF SD Negeri 101877 Tanjung Morawa during the covid19 pandemic. Meanwhile, the use of WhatsApp accounted for 69.1% of teacher performance, with the remaining 30.9% influenced by other factors. Keywords: WhatsApp social media, teacher performance, covid19 pandemic

This study aims to: (1) produce a problem based learning based worksheet that is suitable for thematic learning in grade 5 of elementary school; (2) knowing the students critical thinking skills by applying the participants worksheets in the class. his student worksheet is compiled using the 4D model of Research & Development. Data retrieval research was conducted at SDN 101877 Tanjung Morawa. The research phase is define, design, develop, and Disseminate. The level of feasibility of student worksheets is obtained from expert validators and practitioner validators analyzed. After being validated and revised, the product is tested on a limited basis on students. The results of the trials were then analyzed to determine the feasibility of the worksheet of students from the perspective of students. Extensive tests are conducted after making improvements from the results of limited trials. The final results of the extensive test in the form of pretest and posttest values were then analyzed and obtained a standard gain value of 0.87 in the high category.