@tophatface sorry this is a long answer. How high a grade is he looking at? If it is grade 7-9 it isn't about quoting a whole quote but embedding parts of quotes in a sentence, showing an understanding of the book/play. As a parent look at the past papers (all online) and look at the questions so you know what they are asking. ie 2019 Edexcel paper for A Christmas Carol asks about fear and gives the extract where Scrooge meets the Ghost of Christmas yet to come. So where else in the novel is fear? Can your child do that? Start at the beginning, mentally work through where fear is shown, which characters? Which scenes? What words can he put in to quote? Always the beginning of the books, the extract and the end. This is a work of fiction, contrived to make you think or feel a certain way.
Here is a section of the mark scheme and a link to the full thing, for the ACC extract on fear, look at how the quotes are embedded in the answers
"the adjective ‘shrouded’ links with death and immediately suggests that the Spirit is totally enveloped in its ‘deep black garment’. This is confirmed with another triplet when the Spirit is described as having ‘its head, its face, its form’ concealed by the covering"
Main themes for ACC are (high level) Poverty (social dissatisfaction with The Poor Laws ie imprisoned for debt just like Dickens' father was), Generosity (Fezziwig invites everyone to the party, the charity collectors trying to make a difference but a decent living wage makes all the difference ie when Scrooge increases Bob's salary, Tiny Tim lives) Greed (does it bring Scrooge joy? No. Marley warns him of his own misery in the afterlife), Regret (Belle, carol singer at door) Moral responsibility (improve the working conditions of the poor, those buying the book were very wealthy, aimed at them, Bob's salary, Bob's name is money) Christmas Spirit, Family (Fred and family at Christmas, lively, fun, Mr and Mrs Fezziwig, The Cratchits poor but happy to be with each other, but also Scrooge becomes a second father to TT, we see Scrooge as a child with the ghost of Christmas past, why? Because this is about Fathers and sons) Redemption (the joy of buying the goose for the Cratchits, the joy of giving) and Time. Google things like quote bank a Christmas Carol etc but school should have provided one already.
None of this is my work, I must credit the incredible Mr Salles and his amazing YouTube channel but most of all his book The Ultimate Guide to A Christmas Carol. Sadly we are now very close to exams so time is against your son, but I do recommend the books/YouTube videos but also the past papers and mark schemes. Mr Salles covers all the books mentioned plus the poetry, he can be watched on at least 1.5 speed if not 1.75 speed to breeze through them. These include quotes.
https://qualifications.pearson.com/content/dam/pdf/GCSE/English%20Literature/2015/Exam-materials/1ET0_02_rms_20190822.pdf