感谢英语牛人帮我检查下面这段话的语法错误

修改稿 Cameron (2001) claimed that there are some benefits for young people to start foreign language study in primary school。For instance,it can improve their listening skills and cultivate the capabilities of pronunciation over a long period of time。However,some problems still cannot be ignored。In most cases,although they start early,younger children are slower than the older learners in grammatic study。Cameron also mentioned that “Learning a second language through immersion differs from learning a foreign language as a subject lesson several times a week”。It is apparent that “immersion” students who study other school subjects also in foreign language are more qualified than students who attend regular foreign language lessons only。译文：卡梅伦(2001)宣称：人在小学时开始学习外语是非常有益的。比如说：经过一定时期的过程,这可以提高他们的听力技能,培养发音的技能。然而,有些问题是不可以忽视的。很多情况下,年少孩子在语法学习方面,是跟不上大龄成年人地。卡梅伦也曾提起：通过本能的外语学习,不同于一周几次外语学科的学习。明显的是,用外语学习其他课程的学生,要优势于只在外语课上学习外语的学生。请注意括号里的内容：Cameron (2001) claims（claimed,过去式） that there are some benefits for young people to starting(此处用start,因为是跟着to使用的动词用原形) foreign language study in the (此处the可以删除,中小学是广泛的说法,不需要特指哪所,所以不用the）primary school,（此处断句。用句号） For instance,it can improve their listening skills and cultivate the capabilities of pronunciation over a long period of time。Whereas（这词不顺,可以用HOWEVER）,some problems are（语法错误,删除ARE）still cannot be ignored。In most cases,although they start earlier（用early,此处没有进行比较,故还是使用原级）,younger children are slower than the older learner(learners,复数) in grammar（grammatic study,语法学习） study。Cameron also mentions(mentioned,过去式) that “Learning (加a)second language through immersion differs from learning s（a） foreign language as a subject lesson several times a week”。It is apparent that “immersion” students who study other school subjects also in foreign language are more qualified than students who only attend regular foreign language lessons。(only 挪到最后,语义更准确。)