FOR YEARS, Elizabeth Heilman felt as though her personal family-planning decisions were a topic of public interest. Her eldest son was an only child until he was 10.
"There was often a silence in which the hanging question seemed to be 'Why just one?' " she says. "The implication was that I was perhaps a bit cold or maybe infertile."
She then remarried and had three children in quick succession.
"The general public response to my family of four seems to be that I am unruly and perhaps don't know about birth control."
Now Professor Heilman, of Michigan State University, provides advice to teachers on how to avoid stereotyping and alienating parents because of the size or shape of their family.
Most teachers are aware of the need for sensitivity around mixed race, same sex or immigrant families. But many, she believes, still harbour prejudices about how a "normal" family should look.
"These days, a never divorced, two parent family with two children is still often called 'normal' in colloquial use, even though less than a quarter of households conform to this model," she says.
This concept of a normal family includes a range of assumptions. For example, teachers often expect all children to be close in age. Many respond to large gaps between siblings with "What happened?" This suggests that the gap is unnatural, immediately making parents defensive.
Equally, many teachers expect brothers and sisters to look alike, even when children have different mothers or fathers.
Highlighting these differences ("are you stepbrothers?") requires sensitivity, as children may feel uglier or less adequate than their siblings. Professor Heilman cites a teacher who asked a clumsy boy whether he had the same father as his athletic brother.
She advises schools to avoid terms such as "stepbrother" or "half-sister".
Families may use just "brother" and "sister", so emphasising the distinction can make children uncomfortable.
Similarly, asking a parent in a stepfamily which children "are yours" can also create unwanted tension.
Embarrassed by their perceived abnormality, children can fail to correct mistaken assumptions, allowing classmates to believe that an older mother is their grandmother, for example, or that cohabiting parents are married.
"This can become a burdensome white lie to maintain in a school setting and intensifies the divide between public and private, home and school,"
Professor Heilman says.
"The family, as a hegemonic ideal and source of stigma and prejudice, needs to be taken very seriously.
"When diverse families can flourish without prejudice, our children will be healthier and we will have a more democratic and just society."
In 2005, there were 283,730 weddings. This was a decrease of 10 per cent on the previous year and the lowest number since 1896.
40 per cent of these weddings were remarriages for one or both partners.
For every 1,000 married people, 13 will be divorced.
One in five divorced people have had a previous marriage end in divorce.
66 per cent of children live with married parents, while 25 per cent live with a lone parent.
The average number of children in a family is 1.8.
Married couples are more likely than other families to have three or more children.
In 2003, 153,500 children under the age of 16 were affected by parents divorcing. One in five was under five years old.
In 2001, 139,000 children did not live with their families. This included the looked-after and those living with adults who were not their parents.
Source: Office of National Statistics
All figures are the most recent available