Deportment refers both to acceptable behaviour and the fashionable and acceptable way to hold one's body. It was taught to young ladies in Europe of suitable rank, both through schooling and through conduct manuals.
In the nineteenth century, conduct manuals for young women, dictating acceptable feminine behaviour, were popular and influential, and were detested by proto feminists such as Elizabeth Barrett Browning, who lambasts the genre in her epic Aurora Leigh: ‘I read a score of books on womanhood / To prove, if women do not think at all, / They may teach thinking’ (I, 427).
The Young Lady's Own Book, a typical nineteenth century conduct manual from 1832, containing a chapter on deportment, is available on Google books.
For a history of deportment, tracing the changes in desirable deportment from medieval times, see here.
The Hulton Archive at Getty Images contains interesting photos of deportment lessons in the 1950s.