Background and Aim: Hearing impairment can effect many educational abilities and will lead in a dealy in his growth. The objective of this research was to study the effect of hearing impairment on mathematical skill of hearing-impaired students of 4^th grade of elementary in contrast with normal-hearing students.
Methods: The project was cross-sectional and the tool used was the international standard booklet of mathematical questions. There has been 35 hearing-impaired students with range of moderately sever-profound hearing loss selected from the 4^th grade of elementary from exceptional schools in Ray, Pakdasht and Varamina, Iran, and 35 normal-hearing students were randomly selected from ordinary schools next to exceptional schools.
Results: By analyzing the outcomes, the normal-hearing students showed a better result in knowing, application, argument in aspects of cognitive in contrast with hearing-impaired students and there has been a meaningful difference (p<0.05). There was not a meaningful difference in mathematical skill between Ray, Pakdasht and Varamina, Iran in hearing-impaired and normal-hearing groups.
Conclusion: The hearing impairment effects learing of mathematical skill. It is important for hearing-impaired students to presentation various methods in instruction in progress deductive thought and cognitive structure and also development in concepts understand in mathematical domain in rehabilitation services.

Background and Aim: There is a relation between language skills and science learning in educational approach. Hearing-impairment and delay in learning of language skills influence the progress of learning. The aim of this research was to study the effect of educational level elevation on growth of mathematical skill. Therefore, third grade hearing-impaired students of secondary school, and forth grade hearing-impaired and normal-hearing students of elementary school were compared in terms of mathematical skill.
Methods: The research was cross-sectional and the internationally standardized mathematics questions (2007) were selected as the tools of the test. The sample included 31 students of 4^th grade elementary and third grade of secondary school with sever hearing loss from exceptional schools, and 17 normal-hearing students were randomly selected from ordinary schools next to the exceptional schools in Robatkarim, Karaj, and Shahriyar cities, Iran.
Results: According to data analysis there was a meaningful difference between hearing-impaired students of forth and third grades and normal-hearing students in the three fields of knowledge, application and argument (p<0.05). There was a significant difference between the two hearing-impaired groups in knowledge (p<0.05), but they had no meaningful differences in the fields of application and argument (p>0.05).
Conclusion: No significant improvement was seen in the mathematical skill of hearing-impaired students by educational level elevation. Writing mathematical books for the pre-elementary courses, revision of teaching methods, and increasing teaching hours are necessary in mathematics.