Long before Dick Wolf created the “Chicago” TV shows — PD, Fire and Med — there was Chicago Ag. Formally known as the Chicago High School for Agricultural Sciences it is a public, four-year magnet school in the Mount Greenwood neighborhood of the 19th Ward on the far South Side, the “best” school in the CPS district, according to Chicago Ag’s version of Dick Wolf: Principal Bill Hook. For the tenth year, Chicago Ag students, along with local chefs and volunteers from the community are putting on an early Thanksgiving dinner for 350 senior citizens in the 19th Ward. Principal Hook tells WGN’s Steve Alexander it is a “farm to table” event in its purest form. Turkeys, corn, pumpkins, pork, eggs and more produced on the school’s 79-acre farm — the only farm in the City of Chicago — are being used to prepare the dinner.