It's very hard for August born children.
My friend's son has been put, for yr 1, into a yr1/R class - he only turned 5 a month ago. Until Christmas in reception, he fell asleep every day after lunch and the (lovely) teacher used to leave him asleep on a pile of teddies. He would frequently cry and tantrum on the way home - just tiredness, he's not a spoilt child. Luckily, they split reception by age at ds1's school, so nobody in his class was born in 2002. All had 2003 birthdays, so the biggest age gap in the class was 9 months. The older reception intake, those with 2002 birthdays, went into R/yr1 class, which comprised older reception and younger year one.
The difficulty comes with always being the youngest, least able, least mature. My brother was like this - had he been born a month later he would have been a perfectly mature and able member of the class below!
HOwever .... I also know a chap who by rights should have been in our year, but as he was born on the cusp he was allowed to stay below ... and throughout school, he always sought boys his own age. i think he felt he had something to prove.
both choices have a difficulty.