commenting too quickly - school situation

Rolled out blogs to all of our year 7 students yesterday and most is working quite well with only small stumbling blocks.

One is the error a user will get when commenting too quickly. In a school situation we have 80 kids with their own laptop - teachers have about 20 per class and want students to comment on a post they have made.

Since it's a confined amount of time - "Ok kids, read this short post and comment, you have three minutes to complete" - some students run into the 30 second time limit between comments.

I imagine this is because WPMU is seeing them all come from the same IP address - but as blogging proliferates I think this will become a bigger problem. Anyway to shorten the time between comments although not sure I want to go down that road.

We can modify our classroom management but any thoughts on how to handle it on the tech/wpmu side?