When I was in junior high school I got free lunch for a while. I worked in the cafeteria to help wash dishes, but in hindsight I'm not sure if that was the reason I got free lunches or not. My dad didn't work much in the 1980's and we had relatively low family income. I may have been benefiting from the government free lunch program.
Free or reduced price school lunches at our nations public schools are part of the National School Lunch Program. See NSL fact sheet You may be surprised how many families qualify for free or reduced lunches. Today a large percentage of families with school age children can qualify for free or reduced lunches. I looked up our local school and found that 55% of the students are eligible for either free or reduced lunch. Another school in the city has 88% of the kids who qualify. Our county has median income that is just about the national average so this is likely not unique.
For a free lunch your family income must fall below 130% of the poverty line and for reduced price lunch the household income needs to be under 185% of poverty. Free lunch is free entirely. Reduced price lunch costs 'no more than' 40¢. Based on the 2012 poverty rates the thresholds would be as follows :
Note these are not the official numbers. I don't know if they've yet defined the rates for the 2012 - 2013 school year. But it will probably be the figures above of relatively close to them.
As you can see in the above table a family of 4 could qualify for reduced lunch with a family income of under $42,000. I would guess that 25-50% of families with school age children qualify for at least reduced lunches. I'm not sure on the statistics cause its hard to find family income data distributions specific to households with children in school. I expect that families with children in school are lower income than older families in general as people usually have peak incomes later in life.