No, There are no need to allow social sites in schools.
The Internet and social networking services have allowed
Do you mean "What should you do if you are not 'allowed' on twitter?" because it seems to me that anyone who is on a social networking site it aloud on it.
Potential employers should be allowed to base their hiring decision on the content found on an applicant's social networking site.
information should you avoid posting on social networking sites?
I think you mean "does social networking cause a decrease in school grades?" If it does you clearly shouldn't use any.
Anyone is allowed to have a Social Networking Account, it doesn't matter. Although it is reccommended by many, that kids under 13 should not necessarily have an account for safety issues and concerns.
no
Schools block social networking websites.
sometimes
There is no official number for how many kids are kicked out of school for social networking. Many schools have filtering software on their networks which prohibit students from even visiting the websites on school grounds.
Birthday
Only if they are responsible!