Baptism was not a new idea ... heaven was opened God’s spirit descended on Jesus God’s voice was heard A dove, often used as a symbol of peace, represents God’s spirit descending on Jesus.
Pupils could be asked if they can see how the trinity is connected to the baptism of Jesus (dove, voice, Jesus). Look at art works - such as the one in the clip - about this Bible story.
Note that Jesus’s baptism marked the beginning of His Messianic ... and he saw the Spirit of God descending like a dove and alighting on him. And a voice from heaven said, ‘This is my Son ...