One of the bigger problems is that I don't see any member for the gender of the kindergartner, even though it is used several times in the program.
I mean, a gender string is declared somewhere, but it's not going to change the problem with expressions like this.
Code:
fscanf(thefile,"%s%s%s%s%d%d%s",kids[i].id,kids[i].name,kids[i].age,&kids[i].weight,&kids[i].height,kids[i].gender);
So you should group all of the data in a single type.
Code:
for(i=0;i>0;i++); {
What is with this loop that doesn't even execute?
Also, listen to the people telling you to format/indent. It's important, especially when you want to show people code.
And, for good measure everyone, I agree with brewbuck. Realistically, the sort of advice I was able to give applies to C and C++ equally. I mean, we can address the issue of not using classes, or iostream objects later. C++ does nothing to stop you from using it this way anyway.