This work studies the social welfare and educational practices carried out by the nuns of “Instituto Coração de Jesus” with children of coal mining workers in the State of Santa Catarina (Brazil) in the 1960s and the 1970s. It studies the pedagogical practices implemented by nuns and lay teachers, recorded in a document entitled Crônica do Jardim de Infância Cristo Rei. The document contains narratives of ten years of work with sons and daughters of workers at Lavador de Carvão – CSN, in the town of Capivari de Baixo (Tubarão – SC), and presents daily activities and several aspects of the Kindergarten routine and life in the village. After a careful study of the document, our attention was focused on the teaching of reading and writing. The teaching of reading and writing was a priority in the 3rd period, i.e., in the education of six and seven year old children, which is confi rmed by the introduction of ABC tests in the Kindergarten since 1961. The ABC tests were used to measure the degree of maturity for reading and writing. Children were classifi ed by different levels of maturity. The process of exclusion created by the results of the ABC tests confi rmed their theoretical bases, according to which biologically immature children are incapable of learning. Considering the information recorded in the document in relation to the test results, it is evident that most of the six and seven year old children reached the average level or above. Cases of children with high and extremely high levels of maturity were rare. However, there were also those who were classifi ed at the lowest level, which is, zero, and even those who were unable to respond to the tests.