By and large, children are not forced to read anything except in school. The gripes against the classics, however, usually stem from (1) young readers' not yet being at the appropriate reading level and (2) arcane references and vocabulary. Consider the following sentence from David Copperfield:
Ham Peggotty, who went to the national school, and was a very dragon at his catechism, and who may therefore be regarded as a credible witness, reported next day, that happening to peep in at the parlour-door an hour after this, he was instantly descried by Miss Betsey, then walking to and fro in a state of agitation, and pounced upon before he could make his escape.
I can easily see a nine-year-old wondering exactly what "national school," "a very dragon," "catechism," "parlour," and "descried" meant and not being able to find all the answers very quickly, even with a dictionary at hand.
Your Moppet May Vary.