Some elements of the story are based on the novel 'The Prince and the Pauper' by Mark Twain, though this sort of situation is more realistically portrayed here than in the source material imo. Also it's with girls rather than boys and the setting is a steampunk Victorian-type England instead of the 16th century England (interestingly the source material was initially conceived as a play and would take place in the contemporary to the author Victorian era, but this was soon changed to the final setting, so this might be the closest in setting to how the initial version would be - Mark Twain: A literary life (2000), p.119-120 - found through Wikipedia).

Is much like Beauty and the Beast (the western title reflects this quite clearly too, since La Belle et la Bête is the original french title of said tale), only in an online world - though it focuses on things other than romance instead.

This is a mecha anime and set mainly on space, and it's said to be very loosely based on Frances Hodgson Burnett's novel A Little Princess and secondarily, according to Wikipedia, also on Little Lord Fauntleroy and Secret Garden. Having read Little Princess and Secret Garden (and seen the anime adaptation of the 1st) I'd say there are some similarities, but they are superficial e.g. the protagonist is called Sarah and has a doll called Emily, and there are characters with names found in Burnett's novels e.g Lottie, Dickon, Lavinia (but she isn't a bully here) e.t.c.

Based on the novel by the same name by British author Joan G. Robinson. This is one of the tamest changes in setting on this list, as the setting is simply moved from England to Japan. Other plot details are also changed however, and, having read the book after watching the movie, I believe that these changes make the movie better than the book.

Based on the play by the same name by William Shakespeare but changes the setting to a fantasy environment. Also changes a few plot details e.g. the current situation of Juliet's family.

Romeo and Juliet, but in a boarding school. Seems more comedic than the original material.

Loosely based on the plays Hamlet and The Tempest by William Shakespeare. The setting is a sci-fi-esque one.

Based on the Count of Mont Cristo novel by Alexandre Dumas, but transfers the setting to space and changes the viewpoint to that of a minor character to keep viewers more in the dark about the actions of the count.

Based on Akita Kurosawa's Film The 7 Samurai, but changes the setting to a steampunk-esque one with robots/mechas.

Based on Akita's Kurosawa's film Yojimbo, but changes the setting to the modern day.

The Odyssey, but in space.

Seems to have story elements similar to Pinocchio, but is set in mordern day Japan instead.