The purpose of this study was to investigate the effectiveness of flipped learning in improving English grammatical performance in speaking and writing of underachieving language learners. The participants of the study consisted of forty nine first year secondary stage students at Port Said military secondary school for boys in Port Said Governorate. The two groups pre-post test quasi-experimental design was used. The instruments of the study included the verbal intelligence test for youth prepared by Hammed Zahran and the pre- post grammatical performance in speaking test and grammatical performance in writing test. The results of the study revealed that flipped learning significantly developed English grammatical performance in speaking and writing of both underachieving language learners and their normal peers.
Keywords: English grammatical performance, flipped learning, secondary stage., underachieving language learners
