The school bell chimed and the class shuffled home.   But the students weren’t little children.   They were Democratic Presidential candidates!   And boy-oh-boy did they get sent packing with a ton of homework!   Teachers, students, parents and community members from all over the country sat them down with instructions on how to improve the public education system.   Kudos to the candidates for agreeing to listen.   It was billed as the MSNBC “Public Education Forum 2020:…