In my opinion, the influencing factors for this survey would have been privacy and time. Many of the students could have been too tired to answer properly, since it was early in the morning (the beginning of school). They could have chosen one randomly or without thinking much about it. Another important factor would have been privacy because the students could have felt pressured to answer a certain way. The first students to answer could have chosen the more expensive one to show off. The others might have felt the need to make the same choice to fit in. Without privacy, there is no guarantee for the truth and what would cause certain individuals to lie.
Do you think 10 out of 800 students is a representative sample of the entire school?
No. there are too many Influencing factors to know for sure what the accurate answer is. Also, ten students is not an accurate representation of a school of 800. They needed to ask more students to get a better idea since the more people they ask, the more accurate their response will be.