Schools are dropping controversial subjects from history lessons -- such as the Holocaust and the Crusades -- because teachers do not want to cause offence, Government research has found.

The way the slave trade is taught can lead white children -- as well as black pupils -- to feel alienated, according to the study by the Historical Association.

And a lack of factual knowledge among teachers, particularly in primary schools, is leading to "shallow" lessons on emotive and difficult subjects.

Some teachers have even dropped the Holocaust completely from lessons over fears that Muslim pupils might express anti-Semitic reactions in class.

And one school avoided teaching the Crusades because its "balanced" handling of the topic would directly contradict what was taught in local mosques.