Question

Invitation to invite a guests to attend a presentation by a motivational speaker of your choice at your school

Answer 1

It would be best if you made such an invitation personal; mentioning your school  specifically. But I can help you with an example

Dear students and teachers!

Do you want to know how to best protect our environment? Do you need the motivation to remember to recycle?

Meet Al Gore, one of the leading voices in the fight against man-made global warming.

Al Gore will give you the motivation you need!