As a mom and an educator, let me tell you what I think is a vital skill for your child to learn before kindergarten. Its not reading, writing, sitting for periods of time....its all about SELF.
I find it so important to help kids develop strong self-confidence and trust in themselves and their environment (including parents, teachers, and peers). This ability to understand their worth, importance, and independence will allow them to explore and take risks to learn new things....and ask for help when they need it.
For example, if a child is willing to try to dress herself and ends up with her pants on backwards...they have learned how to use body coordination and planning to put her feet through the right holes, pull up the top, stand up, and get it to feel right. She has also learned that she can do it by herself. This will help her realize she can do a lot of other things on her own (like read a book or write a story). Think...if an adult comes up to her and says 'that's wrong', the child now looses that sense of accomplishment and will feel that she cannot be successful at doing things on her own and taking a risk is not worth it.
Why is risk-taking important? Because you have to take risks to learn new things. To decide that you want to read a book...you have to take the risk that you can't do it right away or you might be wrong. You must also take a risk in order to ask questions or ask for help. If you have a strong sense of self....you understand that you can try anything but it might not work out, at least the first time, and that is ok!
Another important element is a supportive and responsive environment. By providing lots of opportunities to try new things, be independent, and find support, a child will feel a sense of security in which to develop. I will use my favorite sippy cup example. Parents love sippy cups. Eventually, a child will need to use a regular open-topped cup. Parents always fear the spill...but if a child never has the opportunity to use a regular cup and experience the risk for that spill...they will never experience success. If they drink and spill...its ok...they will learn to try a new technique next time and that if they spill, they will have to help clean it up. Congratulate them in trying and kindly help them clean up.
Kids learn a lot in many ways and in lots of unexpected places. I wish parents would focus more on their children's self-development over 'academics'. Children will be taught to read and write in first grade, they will be taught to add and subtract, they will be taught the names of the 50 states. But, they will not be as nurtured in their development of themselves and THIS development is essential in being academically successful.