This passage is meant for year 2 students. Please edit if for me. Any comments to improve the passage are welcome.
I have no idea what age or stage year 2 represents where you are. In the UK, Year 2 pupils are 6 years old. I would imagine you don't mean them!
One day, Tony went to a shopping centre with his parents. It was very crowded there.
Tony saw a toy displayed in the window of one of the shops. He liked it so much that he quickly walked to the shop. [I would tend to use 'ran' or 'hurried', or at the very least 'walked quickly'. I'd probably use 'into' rather than 'to', otherwise it sounds like the window is some distance away from the shop.] After looking at the toy for some time, he turned around to find that his parents were missing. His parents did not know that their son had wandered off by himself. Tony panicked as he could not find his parents. He was soon crying [I would tend to say "He began to cry" or "He soon began to cry".]
A young man saw him crying, and asked him what had happened? [not needed in reported speech] “I can’t find my parents,” he explained, tears flowing down his cheeks. “Don’t worry. I’ll help you.”
The young man told him to wait outside the shop with him as he believed his parents would be [I'd probably say "he thought his parents might be / would be"] looking for him. [It's a bit confusing with he/his. Would it be better for the helpful stranger to be a woman instead of a man?] About five minutes later, Tony saw his parents. He was relieved [A very mild reaction for a frightened child! At the least, I would say "He was hugely relieved"]. His mother said, “You made Father and me look high and low for you. We were so worried.”
Tony apologised to his mother and promised her that this [I would use 'it'] would never happen again.
He has learnt his lesson. Nowadays, he stays close to his parents whenever he goes shopping with them.