Just for another option I will go a completely different route. I will design a Likert test. A Likert test is where you rate 1 as bad and 5 a super with other intergers in the middle. You can then survey the population of the school by giving them this question "How do you rate our food?" Then you can calculate the average score for the rating. The closer to 5 the average is, then the better the food is, the closer to 1 the score is the likelyhood that the food quality will need to be increased.