History teacher. So, re: the video:
The ex-headmaster hasn't actually read the book he's commenting on. Generally, as a historian, if we're going to look at a source like, oh I don't know, a text, we actually read it rather than imagine what it might say.
Decolonising the curriculum doesn't mean that you 'forget everything that happened in the 100s and 100s of years before [empire]'. It's not possible because otherwise you can't explain empire.
More worryingly, the two people in the video don't seem to know their history. 43AD Romans (lot of evidence of international migration across that particular empire that filtered into Britain) and they gave us our name, i.e. Britannia. The Anglo-Saxons (so also not Britons) are a bunch of Jutes, Angles and Saxons (oddly enough) who invade once the Romans leave, and they're followed by the Norse crowd who are basically Danes of one description or another - often (mis)known as Vikings. These people establish Dane Law (you know, what with them being Danes) in huge swathes of England until this is wiped out by William Duke of Normandy (1066 and all that). Last time I looked, Normandy was still in France. So that's got us 1,000 years with most of our leaders not even able to speak English ... And to the Tudors (mercantilism > beginnings of empire > industrial revolution). There's literally no part of this history where I can point to 'British' being the dominant culture.
Those 'medieval churches' he's going on about are Norman churches. Most of our laws (whether it's the common law tradition of Dane Law or the statute tradition of Feudal law) are imported. All the archaeological evidence points towards large scale movements of people across continents - for example, the 'ivory bangle lady' (black Roman in York circa 350AD) or John Blanke (black musician in Henry VIII's court) or Francis Barber (black man who incidentally invented the idea of the English dictionary with Samuel Johnson and helped write the damn thing - 1755).
"Research by Policy Exchange has found that amongst PGCSE programmes analysed, trainees receive on average just 17.8 days of subject specific training over the course of a yearlong programme. This means that too many new teachers lack the subject specific pedagogical knowledge to critically evaluate training and resources and ensure their teaching remains impartial."
Firstly, Policy Exchange was founded by a Conservative MP and the Daily Telegraph reports that it's the largest, most influential think tank of the right. They exist to advance the policies of the right. They're not a neutral source of information.
Secondly, why would you need more than 17.8 days of subject specific training on a PGCE? I spent 3 years doing an undergrad in history (I got a First) and a year doing a Masters in history (I got a Distinction). I already have 4 years of subject specific training. Isn't that enough?
You'll then notice the clever sleight of hand: 'This means that too many new teachers lack of the subject specific pedagogical knowledge ...' But they've not said how many days were spent training 'pedagogical knowledge'. You think it's 17.8, but that refers to subject specific training (i.e. history) not pedagogical knowledge (i.e. how to teach). Obviously, as someone who studies sources closely, I can see where they've tried to twist the evidence so that it matches the message they want to convey. And this is exactly what we teach in our 'woke' curriculum: 1) What's the source? 2) Who made it? When? Where? Because this will reveal the bias. 3) Why was the source made? To inform? To persuade? Once us 'woke' teachers have got the kids to figure this out, they'll be able to see that a right wing think tank is trying to influence education for their own ends.
^^ In other words, it's unsubstantiated opinion, using twisted facts, to try and create a narrative designed to attack the discipline.
If you were one of my students, I'd be worried that your approach would barely scrape you a pass at GCSE.