I have read on various occasions that the quality of IGCSE's are not comparable to (lower) than the UK GCSE. Here are some articles that may make you question that assumption. In fact IGCSEs are known to be much more rigorous than GCSE being more comparable to the old GCE O level.
Many schools in the UK are actually moving to the IGCSE and the IB in favour of the existing GCSE and A levels as their quality is dropping.
PS I am not a school teacher and have no personal interests other than educating myself on seperating fact from heresay.
http://www.dailymail.co.uk/news/article … evels.html
also
http://news.bbc.co.uk/2/hi/uk_news/educ … 924496.stm (note this is an old article and changes have been made to say speaking in French, etc)