Jumping to various functions MIPS

So I am new to MIPS and I wanted to implement simple modulo arithmetic functions. I am unable to see why the program is not jumping according to the jump statements in the code. Any help would be appreciated.

    .data
text_enquiry    :   .asciiz "Enter operation code (1-add, 2-subtract, 3-multiply, 4-exponentiation, 5-inversion, 6-exit): "
text_a          :   .asciiz "Enter a: "
text_b          :   .asciiz "Enter b: "
text_m          :   .asciiz "Enter m: "
text_result     :   .asciiz "Result = "
new_line        :   .asciiz "\n"

    .text
main:

    ##  t0 = code, t1 = a, t2 = b, t3 = m

    #print operation message
    la      $a0, text_enquiry
    li      $v0, 4
    syscall

    #read code
    li      $v0, 5
    syscall
    move    $t0, $v0

    #if code == 6
    beq     $t0, 6, exit
    j       rest

exit:
    li      $v0, 10
    syscall

    #else, continue procedure

    #print 'a, b, m' messages and read them
rest:
    la      $a1, text_a
    li      $v0, 4
    syscall
    li      $v0, 5
    syscall
    move    $t1, $v0

    la      $a1, text_b
    li      $v0, 4
    syscall
    li      $v0, 5
    syscall
    move    $t2, $v0

    la      $a1, text_m
    li      $v0, 4
    syscall
    li      $v0, 5
    syscall
    move    $t3, $v0
    j       mod

    ##  t0 = code, t1 = a, t2 = b, t3 = m, t4 = un-modded result, t5 = modded result, t6 = 
mod:
    beq     $t0, 1, func_add
    beq     $t0, 2, func_sub
    beq     $t0, 3, func_mul
    # beq       $t0, 4, func_exp

func_add:
    add     $t4, $t1, $t2
    div     $t4, $t3
    mfhi    $t5
    #print accordingly
    la      $a3, text_result
    li      $v0, 4
    syscall
    move    $a3, $t5
    li      $v0, 1
    syscall
    la      $a3, new_line
    li      $v0, 4
    syscall

    j       main

func_sub:
    sub     $t4, $t1, $t2
    div     $t4, $t3
    mfhi    $t5
    #print accordingly
    la      $a3, text_result
    li      $v0, 4
    syscall
    move    $a3, $t5
    li      $v0, 1
    syscall

    j       main

func_mul:
    mult    $t1, $t2
    mflo    $t4
    div     $t4, $t3
    mfhi    $t5
    #print accordingly
    la      $a3, text_result
    li      $v0, 4
    syscall
    move    $a3, $t5
    li      $v0, 1
    syscall

    j       main

As you can see, the code works fine when the code is '6' but doesn't work for any other code value.