At an education select committee hearing, senior Ofsted inspector Sue Morris-King said the inspectorate is ramping up its scrutiny of off-rolling, which includes attempts by schools to encourage parents to home educate challenging children.
The action follows recent concerns raised by the Association of Directors of Children's Services (ADCS) and the Children's Commissioner for England.
She said that inspectors have recently undergone specialist training on the issue to help them better challenge schools where off-rolling is suspected to have taken place.
The issue will also form part of next year's inspection framework. In addition, inspectors are taking into account incidents of off-rolling when delivering their judgment on schools.
"If we find parents being pressured to take children off roll during inspection that is strongly challenged and will be taken into account in the inspection judgment being made," she told MPs.
"We are looking more closely at off-rolling and how we can get that looked at more closely in our inspections and that is being considered in our 2019 framework.
"We've just had training conferences for inspectors across the country and off-rolling was a part of what featured in that training for inspectors to make them more aware and more able to challenge."
Also at the committee hearing, ADCS president Stuart Gallimore welcomed Ofsted's desire "to get a grip on this issue, particularly where children are being off-rolled in year 11 prior to doing their exams".
He added: "We know there are instances where parents are encouraged to home educate, regardless of their ability or appropriateness of that as a proposition."
Off-rolling is among issues being considered in a government review into school exclusions that launched in March and is being led by former children's minister Edward Timpson.
In its submission to the review the ADCS said it is concerned that such informal exclusion strategies are putting children's safety at risk.
"Increasing numbers of children and young people are slipping under the radar and are missing out on education as a consequence of a number of borderline-improper or actually unlawful strategies such as part-time timetabling, managed moves, encouragement to home school or other types of informal exclusion activity which is not captured in national datasets," the ADCS submission states.
"Further, being in education is one of the strongest protective factors for vulnerable children and young people. Exclusion can exacerbate safeguarding issues, such as gang involvement, and there is a well-proven link between offending behaviours and not being in suitable, full-time education or training."