In small families, it is the oldest child who is the MOST SUCCESSFUL. There are high expectations placed on him/her. H/she is seen as the leader & standard bearer of the family. H/she is encouraged to be a leader, both at home, school, & in other activities. As the oldest, h/she feels that h/she must be first, the best, & to...WIN! H/she is oftentimes an overachiever & ambitious which translates into success in school & later in his/her career.
Conversely, in small families, it is the youngest child who is the LEAST SUCCESSFUL. Although there is more equal treatment of oldest & youngest child in small families, h/she does not have as high expectations placed upon him/her like his/her oldest sibling. H/she is in the more passive role in the family. H/she is comfortable being in the shadow of his/her oldest sibling or perhaps, h/she is so daunted by being in the shadow of his/her oldest sibling, h/she feels like second best & cease trying. Many times, h/she just coasts along in life.
In large families (6-more children per household), it is the youngest child who is the MOST SUCCESSFUL. H/she has myriad opportunities that his/her oldest & older siblings DON'T & WON'T ever have. H/she oftentimes have more fortuitous socioeconomic circumstances where h/she was born so h/she had the opportunity to pursue advanced forms of education. If his/her parents didn't send him/her to college, then it is the oldest & older siblings who sent him/her to college. With an advanced education, h/she will obtain a great job & become successful.
Conversely, in large families, it is the oldest child who is the LEAST SUCCESSFUL. H/she has onerous adult responsibilities placed upon him while still a young child. H/she oftentimes must curtail, even derail his/her goals, placing the family's needs first & foremost. Many times the oldest child must forgo his/her education in order to work to supplement family income. Also, h/she must even curtail his/her aspirations & goals because of other family responsibilities to parents & siblings.