Clear Stats and Remove Opening Page Ads

Please HELP!!

I am using this forum in a 5th grade elementary school setting. I used this forum with my students last year and found the statistics very useful in monitoring the student's use and frequency. The student's loved the site and enjoyed doing some of their writing assignments this way.

This year, I have a new group of students. I would like to clear all the statistics from last school year and have a clean slate to monitor the new group's results. I've searched the FAQs and poured over the functions in the Administration Panel and cannot figure out how to clear statistics? Any ideas?

Also, I bought enough credits to remove the ads for a year, as this is a concern for many of the parents. My intent is to have a closed forum (meaning only available to teacher and students, no guests) for the safety of my students and for their parents' peace of mind. The problem is, when my kids type in the domain name, the first screen, the one they login on, still has ads up at the top. When I look in the Administration Panel it says:
"Ads are disabled for your members until 14 Sept 2010"
"The ads are not disabled for your guests"
Will paying extra for ads to be removed for guests turn the ads off on that opening screen?

Can anyone please help me resolve these concerns?