Thank you so much, Musou_Mitai
and Musou_Mitai's co-worker, for the extensive research on the meaning of Silver Spoon!!
I'm reposting below from my post on chapter 2 discussion thread. ^^
...Meantime, here is my wild guess about the meaning of Silver Spoon for this series, and it's coming from Arakawa-sensei's semi-biographical farmer comic book, 百姓貴族 (Noble-Farmer). In it she describes the life as a farmer based on her experience of growing up as a farmer in Hokkaido, getting up before dawn and working till late into evening. But, they eat the best tasting veggies, eggs, milk, and other crops and farm products; even the crops they don't produce, they can still get the freshest tasting one because other farmers would provide that in exchange for things they don't produce such as milk, eggs, etc., or, they get beef, pork, chicken in similar fashion, (note: and in case of Hokkaido, some of farmers may do similar in-kind exchanges with near-by fisherman as well, and hence get fresh Salmon, Northern King crabs, lobsters, etc. I know some do.. ^^) thus, according to Arakawa-sensei, they ate as if kings & queens and other noble aristocrats. ...Hence the title of her comic, Noble-Farmer, or Farmer-Nobles.
...therefore, I'm guessing the Silver Spoon in this manga may have the similar meaning. We know from their introductions, almost all of students there at Dai-Ezo Ag high school are sons and daughters of farmers. Families they might work their butts-off, but they eat the best tasting crops and other farm produces, like rich aristocrats, and they are born into these families, hence...like, born with Silver Spoons in their mouths....
Then again, I may be completely off.
Anyway, it's kind of fun to guess it's meaning. ^^