This study aimed to compare the deviations in the prepositional usage of first year secondary school learners of English as a Second Language (ESL) in public and private schools. Informal interviews were conducted with the teachers of the subjects for information on the students’ proficiency background as well as the topics they discuss in their English classes. A pilot testing was conducted in a class of 41 high school freshmen of Don Bosco Technical College in Mandaluyong to measure the time limit and expected output of the students. A formal free-writing test was administered in two separate classes with a total respondents of 99 (51 public school students and 48 from private schools). The outputs were checked through manual checking and were measured statistically through T-test. The findings revealed that despite lengthier outputs, private school students committed less errors in their compositions than those from the public schools. However, the errors did not have significant difference statistically. The study also proved the researcher’s hypothesis that L1 (a respondent’s first language) interferes in the use of English prepositions among ESL (English as Second Language) learners.