The quality of education is a key factor in the social development of the individual, society, and the state. This article is aimed at identifying the theoretical essence of the concept, the “quality of education” in the context of the international PISA comparative study and the ongoing education of math teachers as a factor in the development of students’ mathematical literacy. The diagnostics for interviewing and questioning teachers, students and parents revealed problems and difficulties in teaching and studying mathematics. A key tool was context analysis of the GGTU Center for teachers’ professional development activities. The Ongoing Education Program “Schoolchildren Practical Math Literacy Formation” presented in the article and the author’s teaching manual “Life as a Math Plot” reveal their practical focus on the development of math teachers’ professional subject competence, on schoolchildren’s math literacy development, and, as a result, a general improvement in the quality of education according to the PISA results.