Only 4 of the 14 children were girls - while the programme aimed to show children from different class backgrounds, equal gender representation was not particularly considered in 1964. Michael Apted has stated that one of his regrets about this series is that he not take feminism into account, and consequently included fewer girls and did not select them on the basis of any possible careers they might choose.
As this was originally conceived as a one-off, no long term contracts were drawn up with the documentary participants. The interviews since Seven Up! have been voluntary, but Michael Apted says the participants are paid for their appearance in each film, as well as equal parts of any prize the film may win.
This, the first entry in the series, is the only one not directed by Michael Apted; instead it was directed by Canadian Paul Almond. Apted was a researcher on this installment and chose the original selection of children.
Although it began as a political documentary, the series has since evolved into an exploration of human nature and existentialism.
The participants were chosen in an attempt to represent different social classes in Britain in the 1960s. The original theme the feature aimed to present was that the UK's class structure was so strong a person's life path would be set at birth: at seven years old, the children's lives would already represent what they would grow up into; that those born into the higher classes of society were assumed to do better for themselves than those from the lower classes. The idea of class immobility held up in most (but not all) cases as the series has progressed: the children from the working classes have by and large remained in those circles, although Tony Walker seems to have become more middle class.