Well done Professor Brian Boyd, for having the courage to weigh in to the highly charged debate on how to achieve a better social mix in schools.

Some so-called comprehensive schools in Scotland no longer fit the founding ideal of schools that serve children from a wide range of backgrounds on an equal footing.

Between some neighbouring schools, a polarisation has occurred, socially and academically, with some middle-class dominated schools getting a reputation for academic excellence and others in poorer areas being deserted by parents who (often unfairly) judge them to be unsuccessful. Middle-class parents are the most likely to use placing requests to get their children into the "good" schools, which makes matters worse.

But would Prof Boyd's proposal that placing requests only be made in certain circumstances actually produce more socially comprehensive comprehensives? Only to a limited extent. The underlying problem is that society has become deeply stratified, with middle-class families flocking together in affluent areas and successful individuals from deprived areas tending to move away from where they grow up. These factors have a huge impact on the social mix in some catchment areas. Only a complex and probably unworkable system of constantly changing boundaries to give a more balanced demographic could address the problem, and even then, it would be impossible to achieve a true mix in some places.

At least now there is the possibility that, through placing requests, social diversity at schools in affluent areas can be improved because children can come in from less well-off areas. It must also be said that parents would understandably feel aggrieved at being deprived of the long-standing right to make a choice about what school their child attends.

Even so, the problem remains that some schools have virtually no social diversity. Part of the difficulty is that parents tend to be influenced by exam league tables in picking a school, which do not give an accurate picture of what a school has to offer. Since schools with a poorer demographic have higher numbers of children leaving at 16, before Highers, the league table measure of how many fourth-years successfully complete Highers in S5 tends to make those schools look less effective academically when that is not necessarily the case.

Just because fewer children are doing Highers does not mean they are not well taught. A highly motivated child with parents who are committed to their education might do just as well at such a school as at a more "academic" one. But schools where fewer pupils go on to do Highers are often dismissed out of hand by parents.

Scotland is one of the world's most unequal industrialised societies. Oxfam reported last year that Scotland's wealthiest households are 273 times better off than the poorest. A true comprehensive system can only exist in a more balanced society, where life chances of children are not determined by social class, but amending placing-request rules on its own is unlikely to provide the answer.