tkinter child program not closed

I have 2 tkinter programs. The main program will have button to open the second program. The problem is when i try to close the child program, the main program is closed instead. I close the second program with command app.destroy(). How to fix this?
Thanks in advance.

All of the programs have this script

from Tkinter import *
import Tkinter as tk
import os

class SeaofBTCapp(tk.Tk):

    def __init__(self,*args,**kwargs):

        tk.Tk.__init__(self)
        container = tk.Frame(self, background="black")
        container.pack(side="top", fill="both", expand = True)

        container.grid_rowconfigure(0, weight=1)
        container.grid_columnconfigure(0, weight=1)



        self.frames = {}

        for F in (StartPage, PageCheck, PageUpdate, PageDigital, PageAnalog,
                  PageResult, PageHasil):

            frame = F(container, self)

            self.frames[F] = frame

            ##self.overrideredirect(1)

            self.geometry("800x480")
            self.title("IC Checker")
            frame.grid(row=0, column=0, sticky="nsew")

        self.show_frame(StartPage)

    def show_frame(self, cont):

        frame = self.frames[cont]
        frame.tkraise()

##frame class

app = SeaofBTCapp()
app.mainloop()