Teacher was teaching Mahabaratha to 6th std students. "Kans heard devaki's 8th son wud kill him. So he put devaki & vasudev in prison. 1st child was born. Kans killed it by poison. 2nd Kans killed by sword. 3rd was born.

At this point a boy raised his hand for a doubt.

The teacher asked What?

The boy said "If kans knew that the 8th son wud kill him, why did he put devaki & vasudev in SAME jail?"
Teacher fainted !
Generation gap ! but common sense !