for my six year if she is late for school because she is dawdeling she obviously needs more time in the morning. So we go to bed 15 minutes early and wake up 15 minutes earlier. if she is late again we just keep moving it up.
but he is six and just learning good habits. you are going to have to have really fgood habits also.
It starts when he gets home from school. go through his bag and address anything that needs addressing (permission slips, lunch money, gym clothes, notes, homework etc) pack it all back up and put it in a good spot.
Ava takes her shoes off and put them in her drawer. if she needs shoes she can put on play shoes. that way if she can't remember where she took them off at least she has her school shoes ready. when it is time for coats and gloves we do the same thing. they only have one coat but they have school mittens and school hat and they go with school shoes. all ready to grab regardless of how they played the afternoon before.
Have his back pack and lunch ready the night before. preferable in a spot with nothing else. this would also be a good place to put coat and shoes.
lay out clothes for the next day. including socks and underclothes.
playtime.
supper and bath
go to bed at a reasonable time. if your child has trouble waking up in the morning move bedtime back some. if he still has trouble getting up move it back more. I highly recommend the book the 7:00 bedtime.
wake up earlier than you think you need to. I get up and pee and wash my face and get dressed. then I get the kids up when I am ready to parent them. happily

sometimes I have to get up a lot earlier than them

wake up your son and do not leave him alone until he is up and getting dressed. do NOT allow him to get distracted. once he is up move him strait to the table for breakfast. once breakfast is done strait to the tooth brush, hair brush whatever else needs to get done.
shoes on. now all he has to do is get his coat and bag and go.
this would be a good time to watch cartoons (I have to have my kids ready and to this point 45 minutes before they leave for school because Ileave for work and their older sister babysits them but she really shouldn't have to deal with a cranky 6 year old) or read a book. not a school book.
10 minutes before the bus comes put the coat on and head out to the bus stop together. wait with him and honestly while he is learning I would reward him for having a good attitude (lets face it getting up and getting ready for school sucks!) I sticker on his back pack, or maybe pins that collect beads. something small and fun. or maybe even a little peice of candy for his lunch box or a peice of gum on the way home.
He is six. you catch or miss the bus together. if he misses give him a ride. no need to punish. its just as much your fault. but stress that next time you need to work together better to catch the bus.
if he is missing because he dawdles you need to work consistantly with him all day every day on staying on task. my six year old is soooooo slow. I have to constantly encourage her to stay focused and keep moving. it takes more energy for me to siomply get her up and dressed in the morning than it takes to get everyone else in the house including the dog ready for the day! but it is my job to teach her how to get herself ready in the morning. this is hard and it has taken me 35 yerars to really get it together because my parents just expected me to know how to do this. (well and growing up in a warmer client it was also easier. no hats or mitten or scarves...the bane of my existance.)
anyway, it is your job to be organized and be very proactive (attatched at the ho kind of proactive) about helping him stay on task and get ready for the day.