Depending on the activities offered within your explicit and systematic phonics programme some children will be ready for the Readies program within weeks (not months)
Parents can use these at home to speed up the process:-)
Before they start Readies they need to understand that:
*spoken words are made up of 'speech sounds' - phonemes - the smallest sound unit
*we represent these speech sounds on paper with letter/s - graphemes
(I call  them 'Sound Pics)
*Sound Pics can consist of 1 or more letter eg /l/ leg /ll/ hill  
*Sound Pics can represent lots of different speech sounds 
(they understand the concept - eg /s/ as in 'sip' or /s/ as in  'is')
*Speech Sounds can be represented by more than one Sound Pic
(they understand the concept eg /s/ as in 'sip' and /c/ as in 'cent')
So they can start when they have finished my 'Purple Code Level' - they will also know Duck Level 1 and 2 Words (can read and spell them)
They need to be able to use Duck Hands, Lines and Numbers 
Here are some of the Green and Purple Level resources in the ICRWY Lessons app.
When ready for Yellow they can start the first book in the 1,2,3 and Away! Series
They (of course) also continue with the Code Levels and Readers.
Miss Emma x