Here is a template from Microsoft office http://office.microsoft.com/en-us/te...i:TC010290551|
but there are others on the office site.
Also google powerpoint rubrics and you will find many that are grade appropriate.
We teach our first graders here to do powerpoints so I am sort of surprised that your school starts in fifth grade. My second graders are currently working or Prezi's which they like much better than powerpoints.
Have fun! he kids will pick it up so fast.