All school staff should be subject to the same, highest level of vetting as teachers, school leaders have said.
Official guidance aims to minimise the number of checks being sought
They say there is the possibility of another Soham-like failure of the system in England.
They argue this is heightened by the drive for "extended" schools that open for longer as a community resource.
The comments come in the submission by the Secondary Heads Association (SHA) to the inquiry into the murders of Holly Wells and Jessica Chapman.
A former Department for Education and Skills permanent secretary, Sir Michael Bichard, is investigating the lessons to be learned.
The two girls were killed by Ian Huntley, caretaker of the local secondary school at Soham in Cambridgeshire, whose girlfriend worked as a classroom assistant in their primary school.
It emerged that concerns about his past behaviour had not been passed on to his employer in Soham, the Village College principal, Howard Gilbert - a member of the SHA.
The association said there were particular circumstances in that case.
"It might be concluded they were so unusual that there are few lessons to be learned and that the system is basically sound," it said.
"On the contrary, SHA believes that this case, despite these particular circumstances, shows that there are systemic failures.
"Ian Huntley should never have been appointed to a position of trust in a school and, if the system had ensured that the school was properly informed, he would not have been."
The SHA called for all school staff to have to undergo the same level of stringent Criminal Records Bureau vetting as teachers - known as an "enhanced disclosure".
Huntley was appointed before the system was amended with the establishment of the bureau and the different levels of disclosure.
The Department for Education and Skills now says it recommends that caretakers be on the list of those subject to the most stringent checks, which include police intelligence on people.
But its guidelines say only that these checks should apply to those "in sole charge" of children and that this would not normally include "cooks, cleaners, administrative staff and technicians, for example".
The SHA said it believed ancillary staff should be included.
It said non-teaching staff "may in fact have more opportunity than teachers to betray the trust that young people may feel confident in placing in them".
"We note that the promotion by the government of extended schools will increase this possibility."
Extended schools are supposed to make more use of their buildings through such things as breakfast clubs before lessons, after-school homework and sport sessions and adult education classes in the evenings.
The SHA called for greater consistency in the rules different police forces have about what intelligence they collect, what they keep to alert them to possible patterns of offending, how long they keep it and what they pass on to others.