Laura is told by Ms. Wilder that there is no certain age one has to be to take the test for a teaching certificate. However, in Laura Ingalls Wilder: Part I (Season 7 Episode 1) Ms. Wilder is speaking with the superintendent of schools and he says the age one needs to be to take the teaching certificate exam is 16. Laura was the best student who was the closest to the required age of 16 so an exception was made as her 16th birthday was in two weeks and a substitute teacher was needed in another town.
The mud on Nellie's face showed far more than what is seen after the mud fight scene.
When the mill stone crashes through the door an injures Charles the door is clearly a break away.
At 19:35 Laura and Pa are talking about Laura wanting to take her school leaving certificate. Laura says Pa was out and working at the age of 12. Pa says that was because he was the man of the house and he had to work to support the family. That doesn't make sense as Pa had an older brother and his father living at home at the time.