It is all about your skills in talking and listening in situations that your teacher will plan for you. You will have done oral tasks in primary school but if you are worried, as they get more difficult in secondary school, remember that many pupils don't like oral work and may worry about it, even if they do not stammer.
Also, if you've had speech and language therapy, then you'll understand more about the importance of eye contact and body language when you're talking, so you may have a skill that the others do not have.
From S1 your teacher will be setting oral tasks for you to do, just as was the case in primary school. It's important that you listen to what you have to do and build up your confidence by taking small steps at a time.
In S1 you may be asked to give information about a topic or directions on a route to a partner. Your partner will have to make decisions about the information you give and respond to it to show that s/he is listening to you. If you are really anxious about talking then ask your teacher if you can be the listener asking questions the first time you do this.
Remember that listening is as important as talking.
It will help to ask your teacher if you can work with a friend. Then you can plan your talk together and you'll feel more confident speaking to someone you know well. Afterwards, think about how you did and be pleased with yourself for having a go at this task. Then think about how you could take the next step.
The next step when you do an oral task may be to take the speaking role and speak for a little longer and perhaps choose another partner. Each time you take part in an oral task, think about how next time you can take another step to challenge yourself a little more.
As you progress through the school, the oral tasks may become more complicated. Look at the video clips to see some of these.