He taught at the Lantern of Knowledge secondary school in Leyton from April 2015 to January 2016, when he resigned before allegedly attempting to join Isis in Syria.
Haque was prevented from leaving the UK and monitored by security services, who later discovered his plot.
He taught boys aged between 11 and 16 at the fee-paying independent school, where he admitted playing an Isis video to pupils.
His trial heard that they were left “traumatised”, and the Charity Commission found he had “grossly abused” his position of trust to exploit access to children.
An investigation into the Lantern of Knowledge Educational Trust, which runs the school, found its trustees responsible for mismanagement and misconduct and directed them to make changes.
The Charity Commission said they had left children at risk of abuse or harm by Haque, violated standards for independent schools and internal policies.
Tim Hopkins, the regulator’s assistant director for investigations, said: “Haque’s action at this charity was appalling.
“It is completely unacceptable for any charity to be associated with terrorism and we are concerned by the corrosive effect this might have on public confidence in this and other charities.”
The watchdog said improvements had been made but that an official warning had been issued.
Umar Haque allegedly showed extremist propaganda to children he taught at the Lantern of Knowledge Islamic school (Google Streetview)
Mr Hopkins said: “We expect the trustees of this charity to learn from the failings set out in our report, and to comply with the required actions to strengthen the charity’s administration. We will closely monitor the trustees’ compliance with these actions.”
Separate inspections by Ofsted have rated the school as “inadequate” or requiring improvement since 2017.
In January 2019, after Haque was jailed, inspectors found a book in the school library promoting violence against gay people, claiming they were against “the natural order”, and saying that adultery should be punished by death.
Despite being unqualified, Haque had also been allowed to teach children at the Ripple Road madrassa in Barking and at a second Islamic school in east London.
A judge said he groomed children to join a “mini militia” and made them keep the training secret from parents.
“His plan was to create an army of children to assist with multiple terrorist attacks throughout London,” said Dean Haydon, head of the Metropolitan Police’s Counter Terrorism Command. “He tried and he did, we believe, radicalise vulnerable children from the ages of 11 to 14.”
Haque planned to launch simultaneous terror attacks on up to 30 targets, including Big Ben, the Tube, Westfield shopping centre, Heathrow Airport, courts, Shia Muslims, journalists and far-right groups.
UK terror plots that were foiled by security services
Show all 14
In a bugged conversation four days after the 2017 Westminster attack, he told a friend he wanted to “launch different attacks in all the different areas”.
“We are a death squad sent by Allah and his messengers to avenge my Arab brothers' blood.”
At the Ripple Road madrassa, he secretly brainwashed 16 children as young as 11 and made them act out terror attacks.
Haque showed children graphic images, including one of a dead boy, saying they would meet the same fate if they did not join him and promise to become a martyr.
One of the boys later told police: “Umar wants a group of 300 men. He's training us now so by the time I'm in Year 10 we will be physically strong enough to fight.
"Umar told us boys he is part of Islamic State and Islamic State ordered him to do a big attack in London."
Subscribe to Independent Premium to bookmark this article
Want to bookmark your favourite articles and stories to read or reference later? Start your Independent Premium subscription today.
