Seamus's mother is very nervous about him attending Hogwarts in earlier years, so it is unclear why she sent him back, or whether he argued with her about it. Either his mother felt he would be safer at Hogwarts, or he went against her wishes. Unfortunately, he is badly beaten by the Carrow siblings, as he insists on fighting against Snape's regime at Hogwarts. I like to see this side of Seamus, especially after his mixed feelings in earlier books.