I see it is very very rare to skip a year in UK whilst it is not uncommon in America or Australia or France. The most commonly cited reason is social and emotional development rather than the academics.
After reading a few research papers found online, it seems very inconclusive, just like any social science and is eventually "it depends".
The US Accelerated Institute advocates skipping.
I am reading its [clearly self-serving] book now and it seems rather logical and aligns with my common sense.
Problem is almost all 7+ preps (Latymer etc) state entry year is strictly by age. 11+ admission policies also state it is essentially by age, except special circumstances and at the discretion of the school. Even the child is absolutely fine coping with a year ahead and can perform well in 11+ assessment, the age policy alone will handicap the child.
Opinions?