Theory:

     “In the playground,” I said. “We’re walking towards the house. Miss Beam is walking up and down the garden with a tall girl.”
     “What is the girl wearing?” my little friend asked.
     “A blue cotton skirt and pink blouse.”
     “I think it’s Millie?” she said. "What colour is her hair?"
     “Very light,” I said.
     “Yes, that’s Millie. She’s the Head Girl.”
     “There's an old man tying up roses,” I said.
     “Yes, that’s Peter. He’s the gardener. He's hundreds of years old!”
     “And here comes a girl with curly red hair. She’s on crutches.”
     “That’s Anita,” she said.
Explanation:
 
This paragraph consists of dialogues between the narrator and the girl.  While walking, the narrator describes the people he sees to the girl. He sees Miss Beam walking in the garden with a girl. The girl's name was Millie, and she was tall and blonde. Millie wore a blue cotton skirt with a pink top. She was the school's Head Girl.
 
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 Millie, the head girl

The narrator then saw an older man in the garden. His name was Peter. He was a gardener and was tying up the roses. The blind girl describes him as very old and says that he is "hundreds of years old"—the expression “hundreds of years old” signifies that he is old.
 
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Peter, the gardener

The last person that the narrator described was a girl named Anita. She had curly red hair and was on crutches. It was her lame day.
 
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Anita, a girl on crutches
Meanings of difficult words:
  
Sl. No.
Words
Meanings
1
Walking up and down Walking backwards and forward
2
Very lightBlonde; yellowish; hair which is very light
3
GardenerA person who tends and cultivates a garden as a pastime or for a living
4
BlouseA kind of shirt worn by girls; Top
Reference:
National Council of Educational Research and Training (2006). Honeysuckle. A Different Kind of School - E. V. Lucas (pp. 56-62). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.