There are 80% children in the 70% mark category. As per the school "The total number of seats available to class Pre-School 2013-14 are 240 (General Category – 156 i.e. 65%; Economically Weaker Section- 60 i.e. 25%; Girl child quota -12 i.e. 5%; Staff quota-12 i.e. 5%)".
For 156 seats, there are 4,143 application (deduct 12 girl child out of this). The probability of your child getting selected is 0.03765!