[handmodel]

The student who enters the classroom has an IQ that follows the same distribution of intelligence of any of the other students. Therefore, one student out of the 145 must have the highest intelligence and the chances that it is student #4, #30, #100, or #145 is the same.

Here is some python code you can run. You can change around the distribution however you want and you'd get the same exact results. The chance that a particular record is the highest in a set of IID variables is not dependent on the distribution itself.

  from numpy import random
  RecordsSet=0
  TotalSimulations=365000
  for i in range(0,TotalSimulations):
      ClassRoomSample = random.normal(100, 15, 144)
      RecordIQ = max(ClassRoomSample)
      NewStudentIQ = random.normal(100, 15, 1)
      if NewStudentIQ>RecordIQ:
          RecordsSet=RecordsSet+1

  print(100*float(1)/145)
  print(100*float(RecordsSet)/TotalSimulations)

A record is set 1 out of every 145 days/classes. Which means in a year/school of 365 days/classes you'd expect a bit more than 2 records on average.