It sounds like you want to homeschool for the rest of the school year.  It's easy to do in CO, especially for the younger grades.  Here is a link to the Colorado Department of Education about how to homeschool: http://www.cde.state.co.us/choice/homeschool_faq.htm  You are suppose to give a 14 day notice, but if your child is not yet 6 you might not need to.  Personally, if my child was reacting that badly I would try to get around the 14 day notice.

Hi!  Tough question!  

You know your child best and know what your child needs, but in my opinion, since we are this far into the school year-only 1 quarter remaining.  I would allow my child to complete Kindergarten and advance to 1st grade in the following year as planned.  

If your child is experiencing feelings of being distraught, frustrated and angry, these are feelings that he needs to manage and it may be important that he masters this skill now before entering into a grade level of importance.  I am assuming that since we are ending the 3rd quarter, you have already discussed your concerns with the teacher, so you understand that he is acquiring skills and relationships with classmates that will carry over into the 1st grade.  

If you have further concerns, not mentioned, you may want to home school the remaining part of Kindergarten, but I feel that it is important that he master Kindergarten skills and that this does not go skipped.  I'm not familiar with CO 1st grade skill requirements, but in my state, it would be of utmost importance that a child is reading well and prepared for 1st grade appropriately.

Best wishes!

You need to go to http://www.hslda.org/ and check out the laws for your state homeschooling is legal but withdrawing is tricky some school offical react stupidly and do stupid thing like calling truant officers or cps .... Join a homeschool group is very helpful and make sure any letter you send to the school for withdrawl is certified mail return etc... here in Texas we are not required to do anything just simply stop sending your child to school. However I sent a certified letter to the head admissions, one to our THSC and one to our homeschooling support group. As a proof that we have offically declared withdrawl from that system. If any problems arises (because I am a member of THSC, http://www.thsc.org/HomeTHSC.aspx?Id=HOME) THSC will provide me with a lawyer to fix the issue etc... membership might be a tad pricey but so worth it :)) good luck in your venture.