Oral work is called 'Talking and Listening' and your teacher will assess this during ordinary activities in your English lessons. It's important to take a 'step by step' approach to your oral tasks from S1 onwards so that you can develop your confidence and get the best grade you can in any exams that you take in S4.
There are a number of different exams that you may take in S4 and courses do vary, so you must take the advice of your teacher. However, it's the oral requirements of Standard Grade that seem to concern students the most, so they are outlined here.
In Standard Grade English, 'Talking' gets one third of the total mark for English.
This is the same as the elements for 'Reading' and 'Writing'. The course usually takes 2 years and you normally start it at the beginning of S3.