Here’s the completed text with the correct words:
Kelly was a clever girl who usually found school boring. Her mother, a single, hardworking assistant, usually got home till late in the evening. Kelly felt a bit unwanted and didn't know where her life was taking her. When a troublemaking group of youths in a classroom one day, everyone blamed Kelly. That declared she wasn't interested in going to school anymore. She started to hang out with a group of troublemaking youths in a park behind the station. Her mother felt Kelly was a graffiti-spraying person, but didn't know what to do about it. Then Kelly met a warm-hearted social worker who gave her a helping hand. She stopped hanging out with her troublemaking friends.
(Note: I made some assumptions to fit the context provided in your text.)