what does the class rank 1 out of 120 mean?

It means that the person ranked 1 has the highest grades of his class of 120.

does that mean i have to make a valedictorian speech at graduation

you need to discuss this with your class sponsor.

The class rank "1 out of 120" typically refers to a student's academic standing compared to their peers in a specific graduating class. This ranking indicates that the student achieved the highest position academically among a total of 120 students in their class.

To determine class rank, schools generally calculate a student's rank by comparing their academic performance to the rest of the class based on criteria such as grade point average (GPA) or cumulative grade point average (CGPA). The higher the class rank number, the better the student performed relative to their classmates. In this case, being ranked "1 out of 120" means the student achieved the top position academically.

It is worth noting that class rank systems can vary from school to school, so it is important to consider the specific criteria and methodology used by each institution.