Parse.com Store data from one object into another object - objective-c

Question

I'm creating an app using parse as the backend, I have three Classes (User,Student,School). I currently have a pointer between the User class and the Student Class so if I enter a new student I can create a relation to the User.
My issue is I am trying to do the same for the School class, this class is a pre-populated class and when I am creating a new student I need to reference that class by school_id that is in the student class as a pointer.
images of my class are
So from the images you can see that the object_id from the user class is the parent_id in the students class. Now I need to have the object_id or school_id from the School class as the school_id in the Student Class.
Expected results:
User"jamiemw" -> Student"johnnie Williams" -> School"Southwind"
below is what I've tried with
PFObject *kid = [PFObject objectWithClassName:#"Kids"];
kid[#"child_name"] = #"Johnnie Williams";
kid[#"age"] = #"14";
kid[#"date_of_birth"] = #"02/27/2001";
[kid setObject:[PFUser currentUser] forKey:#"parent_id"];
//this is what does not work.
[kid setValue:[PFQuery queryWithClassName:#"Schools"] forKey:#"student_id"];
[kid save];
PFQuery *query = [PFQuery queryWithClassName:#"Kids"];
[query whereKey:#"parent_id" equalTo:[PFUser currentUser]];
[query findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error)
{
for(int i = 0; i <= results.count; i++){
NSLog(#"%#", [results objectAtIndex:i]);
}
}];

Answer 1

Your first problem is that [PFQuery queryWithClassName] returns a PFQuery, as shown in the documentation. Storing this instance of a query is probably not going to give you any useful information, so you will want to first perform the query you instantiated and extract the desired data from that before saving it to a key in the kid PFObject.
The second problem I noticed is that there doesn't appear to be a key student_id for any of the tables you posted screenshots of above. I'm assuming this was a typo and you meant to write [kid setValue:[PFQuery queryWithClassName:#"Schools"] forKey:#"school_id"];
Replacing the above mentioned line of code with the following should achieve the desired result:
[PFQuery queryWithClassName:#"Schools"];
[query whereKey:#"school_id" equalTo:#"southwindE123"];
// getFirstObject can be used here because school_id
// is assumed to be a unique key
PFObject *school = [query getFirstObject];
[kid setValue:school forKey:#"school_id"];