One square meter of land that is planted with rice produces about 5200 kJ of energy per year. A chicken farm produces about 800 kj/m2 of potential food energy per year.
Assume that a human must consume 2400 kJ per day to survive, although it is an oversimplication to imply that a person could survive by eating only one type of food, compare the area of land needed for rice and for chickens to support the student population of a 500 student school for a year.
This problem is just a conversion problem. We must convert the number of students to energy per day, the energy per day to energy per year, the energy per year to square meters for rice and then compare it to square meters for chicken.
(2400kJ/student/day)(500 students)=1.2 GJ per day
(1.2GJ/day)(365.25 days/year) = 438 GJ per year
for rice (438 GJ/year)/(5200 kJ/year/m2) = 84,230 m2
for chickens (438 GJ/year)/(800kJ/year/m2) = 537,500m2
So, it would take 6.38 times as much space to raise the requisit number of chickens.
Of course this does not take into account the amount of space it would take to produce the food to keep 537,500 m2 worth of chickens alive!