Como diz o dlanod em sua resposta, o estudante foi evacuado através da pintura na Sala Precisa que levou ao Cabeça de Javali, a desaparecer de Hogsmeade (ou presumivelmente ser apanhado por pais ou parentes; talvez o Expresso de Hogwarts tenha sido chamado para servir) Isso ocorreu antes da Batalha de Hogwarts.
‘There’s a way,’ said Harry quickly, and he explained about the passageway leading into the Hog’s Head.
‘Potter, we’re talking about hundreds of students –’
‘I know, Professor, but if Voldemort and the Death Eaters are concentrating on the school boundaries they won’t be interested in anyone who’s Disapparating out of the Hog’s Head.’
‘There’s something in that,’ [McGonagall] agreed.
Deathly Hallows - page 479 - UK - chapter 30, The Sacking of Severus Snape
Eu pessoalmente não consigo encontrar nenhuma referência canônica para os Lufa-Lufas em maior número. Ernie Macmillan e Hannah Abbott são mencionados durante a Batalha de Hogwarts. Zacharias Smith trancou:
Harry saw Zacharias Smith bowling over first-years to get to the front of the queue...
Deathly Hallows - page 492 - UK - chapter 31, The Battle of Hogwarts
É mencionado que os Ravenclaws e Grifinórios ficaram para lutar:
Slowly, the four tables emptied. The Slytherin table was completely deserted, but a number of older Ravenclaws remained seated while their fellows filed out: even more Hufflepuffs stayed behind, and half of Gryffindor remained in their seats, necessitating Professor McGonagall’s descent from the teachers’ platform to chivvy the under-age on their way.
Deathly Hallows - page 491 - UK - chapter 31, The Battle of Hogwarts
(Você pode ver que mais Lufa-Lufas ficaram do que a Corvinal e metade da Grifinória ficaram; não está declarado de qualquer forma se a metade da Grifinória que ficou numerada mais do que os Lufa-Lufas)
Voldemort afirmou que os Sonserinos se juntaram ao seu lado depois de deixar o Grande Salão.
‘If your son is dead, Lucius, it is not my fault. He did not come and join me, like the rest of the Slytherins. Perhaps he has decided to befriend Harry Potter?’ (Voldemort)
Deathly Hallows - pages 515-516 - UK - chapter 32, The Elder Wand
Se isso era verdade ou não, eles voltaram para Hogwarts e lutaram contra Voldemort ao lado de seus colegas.
JKR: A part of the final battle that made me smile was Slughorn galloping back with Slytherins, but they’d gone off to get reinforcements first, you know what I’m saying? But yes, they came back, they came back to fight, so I mean- but I’m sure that many people would say “Well, that’s common sense, isn’t it? Isn’t that smart, to get out, get more people and come back with them?”
J.K. Rowling - Pottercast No. 131 - The Leaky Cauldron - 01.02.08
Espero que isso não seja muita informação!