To get the median of a set of data, is to get the middle number. So the nurse would have to get all of the students heights and arrange them in order. Unless we're talking about the mean of the data. Then she would still need to collect the heights of all the students, but then she would need to add the heights together and then divide by the number of students in the class: 35. If we are just talking estimates, I would suggest taking the 3 tallest students and the 3 shortest students and figuring out the mean of that set to estimate the medium height of the class.