Montessori School Escape

Montessori School Escape is another new point and click type room escape game by 123 Bee. I went to my sister’s school to pick her up. I went inside her classroom in search of her but to my surprise no one was there. Thinking that she might have gone with my dad I decided to leave, but the door got locked automatically. Now I am trapped inside the class room. Can you please help me to search for the key of this room? Good luck and have fun!