The groundbreaking study -- believed to the first in Canada to look at the long-term impacts of family upheaval on educational attainment -- found children who experience changes to their family structure are much more likely to become high-school dropouts than classmates whose parents stay together.

The findings were particularly grim for children who live through three or more parental changes, such as divorce or death, remarriage and another divorce. Such children have just a 40% chance of completing their high-school diploma, a success rate half that of children with no upheaval.

"This is a long-run picture, where we can look at number of changes a child experiences and link it to how they finish up as they enter into young adulthood," said Lisa Strohschein, a professor at the University of Alberta, who co-authored the project. "We hope the more of these kids we can get to finish school, the better position they will be in to get into post-secondary education and find good jobs."

The study, considered especially relevant at a time of high divorce rates and increasingly complex family relationships, is published in the new edition of Canadian Journal of Sociology.

Previous research has linked family breakups with negative outcomes for children, but such work usually focuses only on short-term impacts, Prof. Strohschein said.

For her team's study, the scholars tracked the lives of more than 9,400 children from birth to age 20. The data was from a group all born in 1984 in Manitoba into two-parent married households.

Of the initial 9,403 children, 7,569 saw their parents stay together, 1,325 experienced one divorce and 172 had a parent die.

A small number, 285 children, lived through two family transitions (divorce and remarriage) while 52 experienced three transitions.

Analysis of the data found children whose parents stayed together were 78.4% likely to finish high school by age 20, well ahead of classmates with one change to family structure.

Interestingly, there was little difference between children who experienced divorce and those who had a parent die. Both groups were about 60% likely to get a high school diploma. Also at around 60% were children whose parents divorced and remarried.

The biggest concern was for those children in twice-divorced households.

"It's that cumulative effect," Prof. Strohschein said. "Things really seem to fall off when there is a loss of a second marital relationship. It's really striking."