I'm at a loss with my 6 year old

I'm not sure who else to ask, because everything we've tried thus far has not worked.Over the last couple of months, my almost six year old (turns six in two weeks) has, for some reason, decided that it's ok to be downright mean to me. He's become indignant, acts like he's entitled to everything (despite the fact that he doesn't get most things he wants), rude to his brother (who is 3 and Autistic and doesn't understand ridicule or that his brother is intentionally trying to be mean).He started kindergarten two weeks ago, and I feel like his behavior worsened when school started. This is not his first experience at this school, or going to school all day, as he attended pre-k at this school. The differences are the teacher, his classmates (which he knows many of from church), and his teacher. He says he likes his teacher, but he's not having fun because they "don't get to play all day like in pre-k".Also, his behavior worsens when we do nice things for him. For example, he's been asking us for almost two years to go visit the space center. Since his birthday is this month and we have a four day weekend, we figured it would be the best time to go. He did have a great time...in between complaining that we weren't buying him everything he saw, intentionally fighting with his brother, and being completely rude to my husband and me.Tonight, I reached my limit after he started throwing things and attitude when my husband asked him to wash his hands. We sent him to bed and he began hitting and kicking the wall. I pulled all of his toys out of his room, along with his "fun" shirts and outfits (only leaving plain shirts, shorts, and pants).We've tried talking to him, and he tunes us out. We've tried reward systems, taking things away, using, being nice, ignoring him, chore charts, routines, etc. I've considered pulling him out of school to homeschool to see if that helps, but I'm terrified.I'm not sure what to do at this point. Any advice is more than welcomed.Edited for typos and to add other things we've tried for him. via /r/Parenting https://ift.tt/2lliPSs