The National Union of Students says colleges must go further than providing the legal minimum amount of security for insurance coverage and protection of buildings and equipment.
It says bringing school pupils from the age of 14 into colleges will increase the risks.
Personal safety in America became a federal issue in the late 1980s after 22-year-old Jeanne Clery was murdered by a drug-addicted fellow student at the campus of Lehigh College, Pennsylvania.
In an echo of the case, Newham College in east London was forced to confront its security provision in 1995 when student Ayotunde Obonobi was stabbed to death at the college gates. Newham now has electronic swipe card entry and manned gates. Students and staff must wear identity badges at all times.
The NUS paper says: "The often-opposed values concerning openness and security need balancing. A college can be equipped like a fortress and still suffer serious conflict between groups of students."
Katt Martin, NUS vice-president responsible for FE issues, said: "We found some staff didn't even know there were 14 to 16-year-olds on the premises.
We are really concerned for the safety of children and their educational opportunities.
"But we're concerned also about FE colleges being places where adult young people can explore issues. Some student unions run sexual awareness campaigns and 15-plus films. We don't want an environment where everyone is only allowed to watch Disney."
The NUS is represented on a Department for Education and Skills working group looking at the administrative issues of admitting pupils to colleges from age 14.
The union says they should be supervised on campus at all times by a person who has been checked by the Criminal Records Bureau. It wants better training of security staff, and the safeguarding of college campuses to be regarded as a specialism which requires specific training.