∴ Its normal curve is symmetrical about the straight line x= 1000,
Also, the number of people with grades between 80- 100 accounts for about 13 of the total number.
According to symmetry, the number of students with a score of not less than 120 is about 12- 13= 16 of the total number of students.
Students with a score of not less than 16× 1200=200 probably have 120.
So the answer is: 200.