If, as you state, all current historians are agreed on a particular theory regarding WW1 I would look to all other sources to provide a balance. Historical theories tend to go in cycles. At one time the Generals involved in WW1 were castigated, today you tell us that is no longer the case. I would not accept verbatim all that I read. I would certainly question everything I read and question who wrote it and why. That would seem a sensible approach as would allowing a child to have access to all available information and views. Only when you have a full picture can you yourself make reasonable judgement as to the veracity of the actual history together with the individual authors and their writings.