Mrs Oleson teaches the children to count to ten in French but she pronounces (and they repeat) seven as "SAYPPT". Seven in French is spelled "sept", however the P is silent and it is pronounced "SEHTT". She also mispronounces "trois" as "twah", omitting the R which is not silent in French. Also, she tells her pupils that their French pronunciation was atrocious when, aside from those two words, it was actually pretty good.
At 21:27 Harriet is talking about the oil painting "The Bathers" by Paul Cezanne. This painting was not created until somewhere between 1894-1905. This episode was supposed to take place before then so Harriet would not know this painting seeing how it would not have been created yet.
All the boys that attend school wear black pants with belts. Belt loops were not invented or put on pants until 1922 when Levi's started doing it. This episode is supposed to take place in the late 1800s so it is not possible to have belt loops on pants.
After Ralph pulls Willie's hair, Laura explains to Ralph that she knew he had done so because she saw him out of the corner of her eye. However, Laura's back is to both Ralph and Willie, and despite her peripheral vision, she would not have been able to see it happen as she claims.
At 29:00 when Albert is talking to Laura he calls Mrs. Oleson Miss Oleson. He has repeatedly done this through the whole series.
When Laura is hoeing her garden at 29:32, it sounds like she is scraping the hoe on concrete or has very rocky soil. Previously, they show the garden and there are no visible rocks in it. A hoe will not make a sound when you are using it in dirt.
At the start of this episode,which takes place around 1886, Laura is telling her class about the "five boroughs of New York City". At the time of this episode, however, New York City consisted solely of Manhattan Island; the Bronx, Brooklyn, Queens, and Staten Island were independent cities, and didn't become boroughs of New York City until 1898.
At the beginning of the episode, Laura refers to Staten Island as being one of the boroughs of New York City. Staten Island was officially called "Richmond" until 1975.
Laura made Almanzo Tarragon Chicken Aspic for dinner, which is meat encased in an edible molded chilled jello-like covering. Aspics did not become popular in the USA until the 1950s and the first refrigerator came in 1913.