Azizi,
Don't know how wide your interest is.
There are a few books on childrens games that are worth looking at if your interest extends to other countries.
'All in ! All In' by Eilís Brady (published by the Irish Folklore Society) is an excellent study of Dublin street games.
There is a beautiful film called 'Dusty Bluebells' possibly available from the Uster Folk Museum.
'Shocking, Shocking Shocking' (The improper play rhymes of Australian children is well worth having though I don't know how obtainable it is. It was privately published by Wendy Lowenstein in 1974 (Fish and Chip Press, 36 Westbourne Street, Prahran, Victoria, Australia.
I remember being impressed by a radio programme on the work done by Father Damien - for a priest he seemed to have won the confidence of the children he worked with. He died, but you can probably find out what happened to his collection from The Vaughan Williams Memorial Library in London.
The main work with children was done by Iona and Peter Opie, but for the reason previously stated I have always treated this with deep suspicion.