Thanks for excellent reply.
In the above link,
you can see following for the dependents in the UK,
"If your dependants are already in the UK with permission, they will be allowed to extend their stay provided they apply at the same time as you apply to undertake a course of study lasting more than 6 months"
In that link nowhere mentioned that, for the dependents already in UK, to extend their visa, main applicant has to be studied in HEI or university but not in private college.
if my understanding is not correct please help me. yes I agree to all your statements for out side people who can come as dependent.
Regarding work rights of dependent in the UK, to know more details we can go through below link and see conditions attached to dependents in the UK.
http://www.ukba.homeoffice.gov.uk/sitec ... olicy1.pdf
Please correct me if my understanding is not correct