Some English teachers need to be more careful with their English
http://www.google.com/search?hl=en&q=%22is+a+certified+english+teacher%22
If you don’t see what could be wrong, then have a look at this much more popular collocation with certified:
http://www.google.com/search?hl=en&safe=off&q=%22certified+nutter%22
Could it be a British and American collocational difference??