The objective of the study was to examine the performance characteristics and differences between English and Oriya medium school children on various cognitive processing, reading, academic achievement, and teacher perception measures. The sample consists of 243 schoolchildren, 120 from Grade IV and 123 from Grade VII from three different schools of Cuttack city in Orissa, India. The children were individually administered the Figure-Copying, Raven's Progressive Matrices, Matching Familiar Figure Task, Serial Recall, Digit-Span, Wechsler's Intelligence Scale for Children, Block Design, Cloze Reading Comprehension, and Oral Reading tasks. Classroom Achievement scores on different subjects and the teachers' ratings about their students were also taken. Results revealed that children reading in English medium schools outperformed their Oriya medium counterparts in some cognitive measures such as Figure Copying, MFFT, RPM, and Digit-Span tasks irrespective of levels. However, the children studying in Oriya medium schools scored higher in Reading Comprehension task and commit less error compared with their English medium counterparts. However, in case of academic achievement measures at primary level, the Oriya medium children performed better in social science, whereas the English medium students excelled in first language and mathematics. The teachers of Oriya medium schools also rated their children better in general conduct, motivation, and effort in schoolwork, whereas, at the secondary level, there was no difference between these two groups in academic achievement or teacher perception measures.