Theory:

     Rucha finally agreed to stand in if no better person could be found. Meanwhile, she would train with the rest of them under the new PT instructor, Prakash Sir.
 
     He was very enthusiastic about sports and drove the children hard — praising, scolding, correcting but mostly encouraging them.
 
     “Rucha, you are nimble and light. You can do better than that,” he told her often.
 
     “How can I do that?” Rucha confided to Aruna. “I will most probably fall.”
 
     “Don’t be silly. We are all trying to better ourselves. You must try too,” Aruna told her.”
 
     “Springfields have a very fast runner in their team.” Shabnam, their teammate informed them. “Has anyone heard about her? It seems they call her P.T. Usha!”
 
     Prakash Sir overheard this conversation. He took a quick decision. “The girls’ relay team, gather here in five minutes,” he called out. All the girls came together. “Girls, I have been watching you all. You need some more practice, more time on the field. You are not doing enough,” he told them. Vociferous protests greeted this. “All right, all right, girls, calm down,” he held up his hands, placating them. “Tell me, what is your goal. To win the race, isn’t it? Not just to make an attempt. To win! Are we agreed?”
 
     The girls murmured their assent.
 
     “I know you have been training. You just need to give a little extra push to your efforts to win. I know all of you have it in you,” he told them.
Explanation:
  
Rucha agreed to come, but only on the condition that if no other better person could be found in her place. In the meantime, she agreed to practise with the others in the team, under the guidance of their new Physical Training instructor, Prakash Sir. He was a person who was eagerly interested in sports, and he trained the children hard — he praised them, scolded them, corrected their mistakes, but most of the time he encouraged them.
 
PT Instructor.jpg
Their new PT Instructor - enthusiastic about sports, encouraged the children always!
 
He told Rucha that since she was lightweight, her movements were also light and she can do much better in sports. Rucha told Aruna secretively that she will mostly fall down and how she could do what Sir told her to do. Aruna replied that she was silly. She added that all of them tried their best and Rucha should try too. One of their teammates Shabnam informed them about their competitor school Springfields team. She said she heard that there was a very fast runner in their team and that she was nicknamed P.T. Usha. P.T. Usha is a well-known sportsperson who is famous for her running skills.
 
Prakash Sir heard what was going on there. He made a decision quickly and asked the girls' relay team to assemble there in five minutes. Once all the girls came together, he started speaking. He said that he had been watching all of them. He pretended to scold them by saying that their practice was not enough and they needed more time on the field to practice. All the girls protested in loud voices. He calmed them down by holding his hands up, and he tried to bring down their anger. He asked them what their goal was - whether to participate in the game or to win it. He asked whether they all agreed that they wanted to win. The girls whispered their acceptance. He finally said that he knew that they had been training. He added that they needed a little extra push on their efforts, to win the game. He also said they all had it in them to win the game.
 
Meanings of difficult words:
  
 No.
Words
Meanings 
 1
enthusiastichaving intense and eager enjoyment, interest
 2
nimblequick and light in movement or action, agile
 3
confidedtrust (someone) enough to tell them of a secret
 4
vociferousloud and forceful
 5
placatingintended to make someone less angry
Reference:
State Council of Educational Research and Training (2019). Term-2 English Standard-6. Think to Win (pp. 101-108). Published by the Tamil Nadu Textbook and Educational Services Corporation.