These children have better narrative comprehension when compared to peers of higher SES. Since 2012, there has also been some research on the Shift-and-persist model, which attempts to account for the counterintuitive positive health outcomes that can occur in individuals who grow up in low SES families. A gap in reading growth exists between low SES and high SES children, which widens as children move on to higher grades. Reading assessments that test reading growth include measures on basic reading skills (i.e., print familiarity, letter recognition, beginning and ending sounds, rhyming sounds, word recognition), vocabulary (receptive vocabulary), and reading comprehension skills (i.e., listening comprehension, words in context). The reading growth gap is apparent between the spring of kindergarten and the spring of first-grade, the time when children rely more on the school for reading growth and less on their parents. Initially, high SES children begin as better readers than their low SES counterparts. As children get older, high SES children progress more rapidly in reading growth rates than low SES children. These early reading outcomes affect later academic success. The further children fall behind, the more difficult it is to catch up and the more likely they will continue to fall behind. By the time students enter high school in the United States, low SES children are considerably behind their high SES peers in reading growth. Home environment is one of the leading factors of a child's well being. Children living in a poor home with inadequate living conditions are more likely to be susceptible to illness and injuries. The disparities in experiences in the home environment between children of high and low SES affect reading outcomes. The home environment is considered the main contributor to SES reading outcomes. Children of low SES status are read to less often and have fewer books in the home than their high SES peers, which suggests an answer to why children of low SES status have lower initial reading scores than their high SES counterparts upon entering kindergarten. Low SES parents are also less involved in their children's schooling. The home environment makes the largest contribution to the prediction of initial kindergarten reading disparities. Characteristics of the home environment include home literacy environment and parental involvement in school. Home literacy environment is characterized by the frequency with which parents engage in joint book reading with the child, the frequency with which children read books outside of school, and the frequency with which household members visited the library with the child. Parental involvement in school is characterized by attending a parent–teacher conference, attending a parent–teacher association (PTA) meeting, attending an open house, volunteering, participating in fundraising, and attending a school event.