Once you're happy with the lead data and are ready to export into your SIS, you can process the export individually or by using 'bulk select'.
After you've exported the lead, you may find that some fields in your SIS are missing data for that lead. This can be caused by duplicate leads in Funnel. For example, a parent might have entered their child's full name in one form, and a shortened version in another.
Try merging the leads in Funnel and then exporting again to your SIS.