Please don't do it.
My brother was sent to a private shcool (he sat the entrance exam as his state primary teacher thought he had a chance of a scolarship he just missed out but my mum and dad decided to make the sacrifice and send him any way) while I went to the local not very good comprehensive.
This still affects our relationship to this day, I feel furious that my parents treated us differently and my abiding memory of our childhood is parents working long hours and not beeing around much inorder to pay for his school fees.
I did fine at the local comp and would even venture that in the end it made me a more rounded person with an understanding of the real world he will never have.
Having been hot housed and pushed accademically from a young age he now doesn't have the slightest interest in the wider world or learning for the pure joy of it, something I have always had.
Sadly history is repeating itself as he has chosen to send dcs private while mine are thriving at their wonderful local state school and very much part of their local community.
The injustice of beeing treated differently is always there and also affected my relationship with my parents.
Give all children in a family equal opportunities or you risk fracturing your family and storing up a can of worm for the future.