If this question concerns posting pictures of team members, then you may need to get permission from parents. I know with our website, since we are technically a school activity, we have to have parental consent to post pictures on our website of team members. We have an
internet permission form that we require each member to have signed and returned before we post any of their pictures online. If you are affiliated with your school and/or are running the site off school's hosting provider, make sure you check with the appropriate individuals at your school regarding their policies.
Concerning posting pictures from events, I am pretty sure that no further permission is needed because FIRST already requires members to sign consent forms for the taking of and use of pictures from events/competitions. I think this would cover your use of pictures as well.
Hope this helps.