I would like to have an example of graduation speech of grade six school.

My goodness, grade 6 speeches? I have no idea what you would say. When I finished grade 6 I just went to grade 7, and in fact didn't have to give speeches until the end of high school.
I suppose say something about the amount of knowledge you have as a group about technology, and how much power there is in all that, but that without wisdom, general knowledge, and caring, power can be a dangerous thing.