Governments in the UK and US continue to be pretty convinced that preschool programs can make a difference for poor kids with poorly educated parents.

Both countries have invested very heavily in Head Start (US) and Sure Start (UK) to help disadvantaged children catch up with their better-off peers by the time they enter kindergarten.

Arguments about their effectiveness following some rather mixed trial results have tended to be more about the fidelity of program implementation or the quality of the evaluation than the value of the underlying principle.

As with all things in the real world, some preschools are bound to be better than others. That being the case, an international group of researchers led by a team from Canada set out to establish whether preschool programs on the ground, even in all their variability, were having a consistently beneficial impact on children’s lives.

In particular, they wondered whether children from advantaged families might be negatively affected by preschool. Might not the universally-accepted standard repress their potential?

Quite why preschools help disadvantaged children is not yet clear. Some believe they provide a more enriching environment than participants would receive at home. Were that the case, it stands to reason that – for the children of the more fortunate – attending preschool could be less enriching than staying at home .

With all such considerations in mind, the research team, led by Sylvana Cote of the Universite de Montreal, looked at data on 1,691 Canadian families with infants. The families were typical of those born in Quebec. Mothers completed annual questionnaires from the time their children were five months old until they were aged five.

They found that children of mothers with low education levels (no high school diploma) were less likely to attend preschool. However, those who did attend were less likely than similar children who stayed at home to become physically aggressive over the course of five years. This was especially true if they started preschool very young. Indeed, children who started preschool before they were nine months were almost twice as likely to avoid developing behavior problems as children who started later.

The researchers also found that preschool did not have any negative effect on more advantaged children. Children whose mothers graduated from high school and who attended preschool were not more likely to become physically aggressive than similar children who stayed at home.

The authors say the message is plain. More disadvantaged children should attend preschool.

Another side to the argument about potential disadvantage was outlined here last autumn by Thomas Cook and Vivian Wong at Northwestern University. Their concern was about the prospects of Latino children who are already under-represented in US preschool programs. How would they and similar populations of disadvantaged children fare if universal standards were to rise? Would they not slip further behind if preschool programs became the norm in the US ? [See: Can several thin reeds ever make a strong policy boat?

• Summary of “The Role of Maternal Education and Nonmaternal Care Services in the Prevention of Children's Physical Aggression Problems” by Sylvana Cote, Michel Boivin, Daniel Nagin, Christa Japel, Qian Xu, Mark Zoccolillo, Marianne Junger, and Richard Tremblay in Archives of General Psychiatry, Volume 64, Issue 11, pp1305-1312.

See also:
The pros and cons of early years programs – where to start! and Getting the measure of the 'mileage' of preschool care