I have gone through your desires. Starting from the age group of 16 to 19, the following topics must be covered as per what I can think of now:
1. Explaining the importance of their life to them, family, future, and others around.
2. Explaining attitude and how it affects us and others.
3. Explaining the importance of time management in life.
4. Explaining how to socialize in life with others.
5. Explaining how to value life.
6. Explaining what kind of people they can meet in their profession.
7. Explaining the importance of grooming and hygiene.
8. Explaining body language with do's and don'ts.
9. Explaining certain common courtesies and etiquette.
To start a session, you can prepare a questionnaire to ask them questions related to their interests and desires in life, then ask them to discuss themselves in front of everyone in whichever language they are comfortable with.
Alternatively, you can do an activity before starting the session to break the ice. Each student can select a partner, both have to talk to get to know each other better, and then introduce each other to the class.
I hope this will cover most of the day because the important point is not to speak, but to make people understand, which takes time as the understanding level of everyone is different.
An advice to you is to go through the Kirkpatrick model to understand the training concept better. Take care.