Theory:

     "Well,"sniffed Ms. English, "this boy," she pointed at Mahesh, "brought me home a few months back but never bothered to cover me properly with the nice brown paper his father had brought."
 
     "Did Mahesh not get scolded and punished in school for that? Justice Mathematics enquired.
 
     "Oh, yes, he was, repeatedly," said Ms. English in a tearful voice, "but all the punishment and scolding slipped off him like water off a duck's back! Not only did he ruin my looks,"she continued, "he also ill-treated me."
Explanation:
 
Ms. English tried to control her tears and sniffed for a while. She then replied to the Justice. She pointed out at Mahesh and started to explain what had happened. It seemed Mahesh's father had brought Ms. English home a few months back. Mahesh could have covered his English book with a proper brown paper; but, he failed to do so.

Justice Mathematics enquired whether Mahesh had been scolded and punished in the school for his non-maintenance of his English book. Ms. English replied to him, 'yes' in a tearful voice. Though he was punished repeatedly, he did let it go as it did not affect him. Apart from the non-maintenance, Ms. English had also suffered due to Mahesh's mishandle.
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Sniff
To stop liquid in the nose without coming out
2.
Water off a duck's back!
Having no effect on someone
3.
Slip off
Take off with ease or speed
4.
Ruin
To spoil or destroy
Reference:
State Council of Educational Research and Training (2019). Term-3 English Standard-6. BROUGHT TO BOOK: Madhumita Gupta (pp. 109-112). Published by the Tamil Nadu Textbook and Educational Services Corporation.