111 the context 0/ on going primary education in Elhiopia, there is a need for internalrnefficiency improvement in order to reduce '>vastage and to attain UPE by 20J 5 which isrnone 0/ the MDG. Previously, there were studies that are conducted on the factors.rnHowever, there were still inefficiencies in primary schools of Ethiopia. The majorrnpurpose oj this study, thereJore, was to identify the major factors that affect the internalrnefficiency oj primary schools in ACA. These major Jactors were revealed using thernopinions oj three respondent groups drawn from both government and non-governmentrnschools. The research method employed was descriptive survey. Data gatheringrninstnlments were questionnaires. In addition, annual efficiency indicator documents wererncritically assessed. Both descriptive and inferential statistics were used to reveal therndegree of influence oj the factors on IEPS in the study area. As a result, school externalrnfactors are Jound common problems Jor both GS and NGS pupils who were at risk ojrnschool dropout and class-repetitions, whereas school internalJactors were not commonlyrnrelated in affecting the IE oj both GS and NGS pupils. The problems that were severe forrnGS pupils were not critically severe for NGS pupils. However, the overall weighted meanrnresponse values Jor school internal and external Jactors were tested using t-statistic Jorrnthe mean oj dependent variables. The statistical test revealed that both school internalrnand external Jactors are affecting the IEPS in the study area at almost the same degree ofrninfluence. The major school internal Jactors Jound in A CA primary schools are shortagernof textbooks, irrelevant curriculum, lack of guidance and counseling services, failure tornstudy hard, and demand Jor repetitions. Whereas major school external/actors such asrnlow-income source and poor education oj parents, influence of unemployed high schoolrngraduate siblings, mobility oj Jamilies from one school attendance area to another andrnthe desire oj pupils to involve in business are found as critical problems that affect thern1EPS in this study area. The problems seem complex and multidimensional and it needsrncomplex and multidimensional solutions that satisfy the need and interests oj the usersrnand implementers. School community alone can not control all problems that are relatedrnto school internal and external factors, because, it needs resources that are beyond theirrnlevel. The best solutions, therefore, are working with a team approach with combinedrnefforts of the school community, the society, the business groups, the local governmentrnand the regional government that are directly or indirectl) concerned on primaryrneducation.