You also have to be a little careful with what the tests that have been done actually measure - both are rather outdated and 'out of context' measurements.
Basically, they require a child to read, or spell, a series of words in isolation - that is reading as in 'decoding', not reading as in 'comprehending'. An 'age' is calculated based on how far through the test your child got, and how accurate their work was. It is quite usual for 'reasonably able' children to get high 'ages', without it indicating 'extreme giftedness' in any way. DD's reading / spelling ages were both around the top available in the test - 14? or so - when she was in year 1, but although she got Level 6 in English overall at the end of primary, she's not 'exceptionally gifted' by any stretch.
Although they are interesting pieces of data, they are not in themselves predictors, or indicators, of 'high ability in English' - which would include literal and inferential comprehension, empathy with characters, ability to explain reasoning using evidence from the text, selection of vocabulary when writing, use of varied advanced sentence structures, knowingly creating an effect on the reader etc etc etc (I could go on).
English is relatively easy to differentiate in class for the able, so year-acceleration for any but the most extreme cases is not likely to be necessary or allowed. (Maths is harder, because of the need for extra 'content' to be accessed)