How Can I Make Spoken English Training Fun and Effective for School Kids?

I am going to conduct spoken English training for school children ranging from standard 5 to standard 12. Could anyone guide me with the best possible activities to make the training session really effective?

Thank you for your support and help in advance.

Kind regards,
Ann

1. Vocabulary improvement
2. Speaking on public topics
3. Group Discussion
4. Slang
5. Differences in UK English and US English
6. Grammar (if required)
7. Keywords (Word groups, Word always come in groups, starter statement, etc.)

There are a lot more activities available. The key is to engage the students in these activities; otherwise, the outcome may be less effective.

With Regards,
Rajkumar