The problem you describe is one that predates discussions about acceptable use policies and blockers - and is one that probably hasn’t been adequately addressed.  Schools are presumed to operate, from a legal standpoint, “in loco parentis” - in the place of the parent.  That imposes a legal standard on the school and its teachers to do everything possible to protect children.  So, schools where doors aren’t locked and it is therefore possible for people to access the building inappropriately are deemed to be operating in violation of this standard and face the possibility of lawsuits and sanctions in the event of a problem (remember the Laurie Dann situation in suburban Chicago several years ago).  As a result, the protection standard now is presumed to apply equally to the possibility of children being unprotected in their use of the Internet - hence the requirement for blocking software.  Children by nature are children - not adults - and they don’t always understand that things they find on the Internet may not be accurate or appropriate to their age and experience.  They do not always understand that things they do on the Internet may make them vulnerable: consider the case of children who post photos of themselves on My Space or Facebook, leaving them open to contact by pedophiles.  If it is the parent’s responsibility to monitor their child’s use of the Internet at home, and the legal standard under which schools continue to operate is “in loco parentis,” then it is logical to assume that schools will continue to be faced with the challenge of providing reasonable access while blocking other.  And many schools have blocked Wikipedia because of the site’s own inability or reluctance to verify the validity of the credentials of those who post to the site.  I don’t think that the issue is either all black or all white - there is room for lots of gray, and the shades keep changing.  Keep in mind - it wasn’t too long ago that we banned children from having cell phones in school on the recommendations of police departments because the perception was that they were frequently the preferred method for drug dealers to make contact.  As cell phone usage proliferated, we changed the policy.  Now many schools require students to keep cell phones turned off - not just on vibrate - and to keep them in lockers, backpacks, etc.  Policies change as we gain more experience.  This will too.

I was still in high school when the Laurie Dann situation happened.  I was living in a Chicago suburb and it frightened my parents because they knew how much I wanted to become a teacher.  Even to this day (especially what had just happened at Northern Illinois) my mother constantly tells me to protect myself and my students.

I think blocking content is necessary for learning institutions.  The modiator should be able to over-ride the blockage, if/when needed, even if the over-ride is time based.

Plenty of site blocking programs will allow a you to set a “timed” limit to the restricted sites.  So the person can still go on and get whatever information they need to (jump on/jump off).

Good point Oceanic, thanks for the information.

I think instructors as well as students should be on a “timed” process.  Instructors need to lead through example.

Schools and the government should block certain parts of the internet from students.  I’m not fond of YouTube, or any other video site, simply because there are videos that are inappropriate - videos showing teenagers beating up on other teenagers, for example.  These types of videos and others influence kids from all ages, and they think it’s “cool” watching such things.  Websites such as MySpace should also be blocked - this type of community is not safe for any child, no matter what age. 

I think the government should do their research to block certain things from students instead of blocking the internet to a point where we can not teach students technology and how it works.