Why is the British Empire erased from history books?

I am a student of A-level history. I have studied the subject throughout my school career, and have never once seen the words 'British Empire' written in a textbook or on a sheet of paper. I first realised it when I was studying the suffragettes at GCSE, and, although the campaign for women's votes reached its height roughly at the same time as the empire became the largest in the history of the world, I never once saw any mention of Britain's imperial role. Now, I am studying totalitarian regimes of the 20th century and the Norman Invasion, and it becomes clear that it's not only the word that is censored from the education system, but an entire era of British history, simply written off as if it never existed. Everything from the 1300s to the 1900s is omitted.

That is, quite frankly, terrifying; that the media practises self-censorship to such an extent in order to abide by the dictates of political correctness that it can deprive a generation of people of any knowledge of five hundred years of history, as if the events of that era never took place. Whatever the intentions of the people involved, whether they are those genuinely interested in community cohesion or hardcore cultural Marxists, there is no excuse for rewriting history - the history that we teach to our children - to suit your own political agenda, or your cultural prejudices. I believe - from my own studies on the subject - that when the British erased the history of conquered peoples through compulsory education, it was known as 'cultural genocide.' Why is it anything less when we do it to ourselves?

Is it because those six hundred years - out of one thousand two hundred in which Scotland and England have existed - were not important? I doubt it. This was the era of exploration, of innovation, of colonisation, and Enlightenment. This was the collapse of feudalism and the rise of capitalism. This was the time of revolutions and of parliamentary democracy. This was the time of the Jacobite Risings and the Bill of Rights, the Ulster Plantation and the Glorious Revolution. This was the time in which the United Kingdom, and then Great Britain, came into existence. Everything which has made Britain what it is today, as part as practical implications are concerned, occured in this era. The modern political system was formed; the major change of religion occured; the absolute monarchy was replaced with a constitutional one; the origins of the Troubles; the end of the old order that had dominated Europe for a thousand years; the creation of the country that we now live in. Why would this be so readily dismissed?

I would not know how to erase the history of any native peoples; nor would I want to. But I would like to know why the cleansing that we practiced, in ages long past, is now being turned on us, in the modern era.