Final answer:
The sentence describes Laurie's misbehavior at home, as indicated by his insolent speech, carelessness with his sister's milk, and impudent mention of the teacher's advice.
Step-by-step explanation:
The sentence "At lunch he spoke insolently to his father, spilled his baby sister's milk, and remarked that his teacher said we were not to take the name of the Lord in vain" tells us about Laurie's misbehavior at home.
The use of the word insolently indicates a disrespectful tone towards his father, while spilling his baby sister's milk suggests carelessness or a lack of consideration for others.
Mentioning the teacher's remark about not taking the Lord's name in vain in this context implies a certain level of impudence, tying back to his general attitude of disrespect.