Students with different language backgrounds may cause certain challenges to some teachers. The purpose of this article is to analyze the problems some teachers may face while teaching the English language at First-grade elementary-high schools in Iran. The impact of this challenge was surveyed by means of a questionnaire to 171 students. The results have been surveyed by SPSS 24 and Cronbach's alpha value. This research suggests that teaching staff in high schools have to solve this problem by evaluating their students' knowledge and presenting extra classes for the needed ones before the start of the new school year. The new language teachers should have a short period of learning course to encounter it wisely.