l agree that any child can be taught particular skills ,but

一、句子成分

　　主句：I agree

　　宾语从句：that any child can be taught particular skills, but to be really good in areas such as music or sport, then some natural talent is required 其中——

　　—第一分句：any child can be taught particular skills 任何儿童都可以给他们教特殊技能
　　—第二分句：but to be really good in areas such as music or sport, then some natural talent is required 但是,为了（使他们）真正擅长诸如音乐或运动领域,那么自然禀赋也是需要的.

　　第二分句的结构是——
　　【转折连词】but
　　【主要成分】some natural talent is required
　　【插入性目的状语】to be really good in areas such as music or sport,

二、不可数名词包括物质名词和抽象名词,talent是抽象名词,因此不可数.

三、but连接的是整个第二分句,只是主要成分then some natural talent is required 被插入性目的状语to be really good in areas such as music or sport 分隔开了.
再问： 老师可不可以把句子改成I agree that any child can be taught particular skills, but then some natural talent， to be really good in areas such as music or sport, is required（对状语的位置我也很模糊不清的）
再答： 句子或短语作状语，前置需要用逗号隔开，后置就不需要了。你这样改只要把把 to be...前的逗号去掉也是对的。前者强调目的，后者是顺便提及。