Ash Wednesday is a Christian festival. It marks the beginning of six and a half weeks of repentance, fasting and abstinence in preparation for the most important Christian festival of Easter.
For Christians, ashes are a symbol of being sorry for things they have done wrong and want to get rid of forever.
Lent begins with Ash Wednesday and lasts for six and a half weeks.
You have suggested in class things you can do during Lent, for example, stop using your mobile phone or try not to fight with your brothers or sisters! What else could you do?