Numerous researches have demonstrated the enormous role of teachers in achievements of students. Educated and motivated teacher that cares about the success of students devotes more effort to preparing the lesson and thus provides the students better conditions for achieving results. The problem occurs when teachers are not equally qualified, motivated and prepared so it is justified to ask why some people even opt for the teaching profession if they have no motivation for this noble profession. The purpose of this study is to highlight the diversities of the admission requirements to teacher colleges in developed and developing countries. Diversity of admission requirements will show that the selection of candidates can affect students' later academic achievements. Comparative analysis between developed and developing countries, precisely Finland, Japan, Korea, Singapore and Croatia, India, Russia and Turkey, determines if there are any differences in the admission requirements among the selected countries. The analysis and the qualitative approach to the statistical indicators of PISA tests conducted in 2012 show which group of countries achieves better results and points to the correlation of students' achievements and the admission requirements. Research results show that the developed countries have strict entry requirements to teacher colleges and have better understanding of the importance of selecting the best candidates into the teaching profession. Developed countries achieved better results in PISA tests which indicates to a connection between the selection of more capable candidates for teaching profession and student achievement. Research confirms that the role of the teacher is very important and that the future reforms of primary education should be extended to higher education, that is teacher education because teachers play a major role in the educational process. [This paper was published in "2nd International Multidisciplinary Scientific Conference on Social Sciences and Arts SGEM2015, Conference Proceedings, Book 1, Psychology & Psychiatry, Sociology & Healthcare, Education" (vol 2, p17-24). Sofia, Bulgaria: STEF92 Technology. doi: 10.5593/SGEMSOCIAL2015/B12/S3.003.]