Describe the difference in David's circumstances regarding his early days and the time he boarded the London Coach.

David, until the age of ten, grows up in comfortable middle-class circumstances. First, he is raised with kindness and indulgence by his mother and Peggotty, and even after his mother marries Mr. Murdstone, his material circumstances remain comfortable. They are those of a child with good prospects in life. He may be treated cruelly by the Murdstones, but he lives in a pleasant home and is sent to be educated at a reasonably decent boarding school.
Not soon after his mother dies, however, the evil Murdstones give up even the pretense of wanting to take care of him. They take him out of school because they decide it is too expensive and with their usual moralizing, tell him he must go to work. Mr. Murdstone says of David's character:

no greater service can be done than to force it to conform to the ways of the working world, and to bend it and break it.

With this send-off, David is bundled on a London coach at the age of ten to work for a living in miserable circumstances. His standard of living and happiness plummets as he listens to the sounds of rats and is thrust into lower class company. As he puts it of his workplace:

No words can express the secret agony of my soul as I sunk into this companionship; compared these henceforth everyday associates with those of my happier childhood—not to say with Steerforth, Traddles, and the rest of those boys; and felt my hopes of growing up to be a learned and distinguished man, crushed in my bosom.