Adding to pal_013168's answer:
--->view founder Colonel Rodriguez's video, bottom of page
By the way, if every illegal disappeared today, tomato prices wouldn't change. Why? Since the 1960's, all harvesting of tomatoes has been mechanized and is much CHEAPER than manual labor.
Most other crops have been automated - plant to harvest - as well by advanced nations with no cheap labor. They're way ahead of us BECAUSE we HAVE cheap labor.
Most of my friends in college were in the U.S. on student visas. They studied just fine without citizenship, got jobs under H1 visas, worked a while and either returned or immigrated LEGALLY to the U.S.
Honestly...WHY would citizenship be necessary for ANY student? Makes absolutely NO sense.
The only long-term help for poor people in other nations is by building up their own economies. Relying on ours is short-term, compromised help at best.