The founders of three illegally-operating schools in Birmingham face being jailed after Nicky Morgan ordered inspectors to draw up a legal case against them.
Ofsted has been told to prepare cases for prosecution against all 18 unregistered schools it has discovered, and all future cases, in a fresh push to stop pupils being exposed to extremist ideology.
Chief inspector of schools Sir Michael Wilshaw yesterday disclosed that three schools that offered a narrow Islamic-based curriculum using anti-Semitic, homophobic and misogynistic material were shut down in the Midlands city last month.
Independent schools offering full-time education in England must register with the Department for Education and accept inspection by Ofsted. Failure to comply can lead to a jail term of up to 51 weeks and a fine.
All cases will go before the Education Secretary, who will decide if a prosecution can then be pursued.
Mrs Morgan said: "Tackling extremism in all its forms is a key priority of this Government and since 2010 I have taken robust steps to tackle unregistered schools and improve safeguarding.
"However, we know there is more to do, and as the Prime Minister has already announced, we will introduce further powers to regulate settings which teach children intensively and to intervene and impose sanctions where there are safety, welfare or extremism concerns. We are currently consulting on these new powers, and I have personally received strong support from community leaders for them.
"In a further step, I have now asked Ofsted to prepare cases for prosecution against unregistered schools it has identified. For a child to spend a single day in one of these schools is unacceptable, and we are acting swiftly and decisively to eradicate them."
A team of six new inspectors will be involved in identifying, investigating and supporting the prosecution of those operating unregistered schools.