there are still disagreements over the best way to teach EVERYTHING
- Not as ridiculous or passionate as about the teaching of reading and writing.
There have been no properly controlled studies comparing the effectiveness of phonics and other methods.
Apart from that, u don't need any research to understand that phonics cannot be of any help for memorising the unpredictable spellings which occur in at least 4,000 quite common English words, like
blue, shoe, flew, through, to, you, too
or freeze, cheap, cheese, these, police, fleece, geese
and especially not for the 300+ horrors like
been/bean, cheep/cheap, jeans/genes, there/their, here/hear .....
Phonics can provide a good start to literacy acquisition in English, but no more than that.
But if u decide to call the whole of literacy acquisition 'phonics', then it will do the job, provided u spend enough time and resources on it.