In 1843 Mack was sent away to school. For Snow this was almost as crucial a break as for Mack. He lost the close companionship of home but found a wider circle of friends as well as the expected toughening up of school. She, at the age of 10, was now largely alone in her studies since her sister, Effie, was only 4. George Eliot found the separation from her brother, Isaac, traumatic: ‘School parted us,’ she remembered 40 years later. Harriet Martineau was another stuck-at-home sister feeling wretched when her brother James was away at school and college. She was agog to know how Snow was reacting to Bro's absence at school:

Snow was readier than either George Eliot or Harriet Martineau to accept that a more important vocation was opening for her brother. Mack, Erny and cousin Godfrey would all write to her from school: Mack rather stiffly as he tried to show off, Godfrey conscientiously and Erny struggling to find things to say but glad of a pretext for not doing his prep. Snow's first novel Framleigh Hall depicts boys’ public schools as necessary but painful places designed to test their courage and masculine spirit and enable them to develop new friendships. But her need to quiz Mack when her publisher wanted her to include more scenes of school life in her novel suggests that he had given her little sense of what life was like at Rugby School in the aftermath of Thomas Arnold's transforming headmastership. The texture of schoolboys’ lives as described in Tom Brown's Schooldays came as a revelation when she read it two years later.

Her isolation after Mack went away to school brought with it a kind of liberation. It was well understood in the nineteenth-century nursery that girls, even if older, could not be seen to outstrip boys at their studies.