Rabindra,
First off, I'll be moving this post to the JFBConnect v2.5 forums directly after I post this message. I'm not sure why you posted in the Community Builder - Enhanced Registration forum, but I don't think it's related.
As for your issue, there are a few ways to store data differently from Facebook into your Joomla site. We'll need a bit more information on what you're trying to accomplish though to help you. What is the student table? Is it from another extension? Also, what version of JFBConnect are you using?
Finally, please post from the account you subscribed to JFBConnect from. Priority support is for active subscribers only.
Thanks,
Alex