This setting is found at:
Configuration -> System Setup -> Enrollment
Force Price Matrix (initial billing) selection for new Enrolments
When enabled (box ticked), this removes the Automatic Calculation and leaves only the Price Matrix for selection of lesson charges when enrolling a student.
Why force selection of lesson price?
This allows greater control over charges and eliminates the element of human error if for example a student's enrolment end date and start date of a new enrolment overlap which would set them on to second lesson pricing when they should be on first lesson pricing.
ON / Enabled
When enabled (box ticked), only the Price Matrix is available for selection of lesson charges when enrolling a student.
OFF / Disabled
This gives the User a choice between Automatic Calculation OR selecting a price from the Price Matrix when enrolling a student.