This is a story about a boy making his dream come true through his own hard work.

【判断】这是一个结构和语义都正确的句子。
如果把making his dream come true through his own hard work 分析为现在分词作定语，则是语义错误的句子。因为这个故事写得太早了，“正在实现梦想的一个孩子”，这样的故事在全世界、在全国，甚至你的学校和社区里面，简直太多了。不需要去写。

只有把 a boy making his dream come true through his own hard work 分析为“动名词复合结构”，语义才允许。因为动名词意味着已经实现了自己的梦想，才需要大写而特写。就是说，动名词没有时间性，实现梦想可以早于这个故事。

This is a story about a boy who is making his dream come true through his own hard work.

【判断】这是一个结构正确、语义错误的句子。错误在于定语从句作定语，跟上面现在分词作定语的分析，同出一辙！