In a statement to MPs, Ms Kelly is set to admit different parts of the system meant to ban sex offenders from schools have not been working well enough.
And she will announce how she plans to tighten up the rules for the future.
We'll have more throughout Thursday's programme - our Political Correspondent Reeta Chakrabarti reports from Westminster
No 10 says Ms Kelly should keep her job, but she is also coming under fire over a range of other education issues.
'Loopholes'
The minister has been under severe media and political pressure since it emerged a fortnight ago that a teacher had been allowed to teach at a Norfolk school, despite being cautioned for downloading child porn from the internet.
The controversy grew with the news that another man with a conviction for child abuse had been cleared to work as a supply teacher in Dorset.
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VETTING AND BARRING PLANS
Single list for people working with children
This list could check against 8m names
"Central barring unit" will assess cases, not ministers
Teachers will apply for a "vetting and barring disclosure"
Barred list continuously updated
Barred list online, instant access
Appeals through Care Standards Tribunal
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The problems centre around two lists - the sex offenders' register and List 99, the Department for Education and Skills' list of people banned from teaching or those banned from working with children.
It has become clear that some teachers appear on the register, but not on List 99.
Ms Kelly will say she has carried out a root and branch review of the vetting system, and will promise to close loopholes.
The system has developed in a piecemeal way over the last 10 years, she will say.
'Coming clean'
Ms Kelly will say public confidence must be restored, and will outline how she will "rebalance" the system to make the safety of children the most important factor.
She will unveil a "major package of measures" based on the Bichard Report into the Soham child murders, and promise new laws by the end of next month.
The Conservatives have accused ministers of being too slow to act on Sir Michael's recommendations and say public confidence in the system has "ebbed away".
Liberal Democrat education spokesman Ed Davey MP said the secretary "has to come clean on the facts."
Senior Labour MP Ian Gibson said Ms Kelly must immediately move to a "zero tolerance" policy to ban offenders automatically, until a new system was devised.
Other pressures
Some believe Thursday's statement is "make or break" for Ms Kelly, who is also facing criticism on other fronts.
Parts of her school reform plans for England will be criticised in a report backed by ex-Labour leader Neil Kinnock and former education secretary Estelle Morris.
Some Labour backbenchers want ministers to hold back on plans to set up independent "trust" schools with more say over admissions, which the government says will help to drive up standards for all children.
On truancy, the Commons public accounts committee says there was a "sudden" 10% increase in the number of pupils skipping school last year, although ministers say attendance levels are at a "record high".
And performance tables have again been criticised as misleading, as new secondary results for schools in England are published.