Micksy: she can decode knight and spray, but gets stuck on said.
The reason for this is simple.
Although the kn, igh and ay spellings are unpredictable, because they are variants for n, i-e and ey (nice, grey), their pronunciations are regular. So children learn quite quickly how to pronounce or sound them out.
The main sound for ai, however, is /a-e/, as in 'main, train, plain', except in 'plaid', 'plait' and the very high frequency word said. That's why many children keeping being stumped by it until they seen enough times times to learn to read it as a sight word. The words which make learning to read English much slower than in all other European languages, the ones that keep stumping children, are all the ones in which one or more letters don't have their main sound.
After the basic phonics stage with regular sounds, children are nowadays taught other pronunciations for many letters as well, e.g. go – do; laid – said, the – he.
When they find it difficult to make sense of a word, they are encouraged to remember and try out the other pronunciations they have been taught as well, but this can be very tedious for both the children and the adults helping them to learn to read.
Many children make much faster progress if taught to recognise the most common tricky words as sight words quite early on. - U could say that they do better with phonics+.
They take note of the letters with phonically regular sounds (e.g. the g, d, l, s in 'go – do, laid – said'), but learning the 100 or so most used tricky words as whole words enables them to move away a bit faster from phonically simple, and often rather tedious, repetitive texts to real stories.
This is pretty much how children have been taught to read ever since reading became more widespread after the printing of the first English New Testament in 1526. But now that 'synthetic phonics' is the officially favoured, best, one and only, nothing but, teaching method, phonics evangelists dismiss the common sense approach as 'mixed methods' or 'guessing' - as very bad indeed.
The simple truth is that English uses phonic and non-phonic spellings. Phonics works beautifully with phonic spellings, but much less well with the non-phonic ones. Most good readers find their own best way of coping with those.