I'm sorry your son is having difficulty in kindergarten. It is not the way you want him to begin his school years.
As for approaching the teacher... Ask her if you can set up a time for a conference. I suggest after school so you won't be rushed. Be open and honest.
Explain your son's problems. Stick to the facts. She might not have background knowledge of the deficiency, so you might have to educate her. If you have any articles or books dealing with the topic that you can loan her, that might help to open her eyes to the situation.
Then tell her how your son learns best. For example, does he learn better in small groups, sitting close to the teacher, with manipulatives, visuals, by example or non-example, through stories, etc.. Really think about this because this will help her when teaching your son.
Ask how you can help. If you have the time, maybe volunteer one day a week or every other week in the classroom. This would allow you to see what is being covered in the curriculum, so you can reinforce it at home. This is not a time to spy on the teacher, but to really help.
Since your son's deficiency will probably play a role throughout his school years, ask what you need to do to start the paper work to get the services he needs. If his is attending a public school, there are many services from extra help in reading, math and writing to speech and even occupational therapy that are free. However, screening and testing need to take place first. The reason I suggest to start now it the process can take several months if not a school year. If he qualifies then a 504 plan can be written up and your son can get help from educational specialists.
Ask the teacher for a plan - one to be followed at school and one for home. Communication is key. You will have to work together in order to do what is best for your son. If you are open, honest and non-judgmental, I'm sure the teacher will be more than willing to do what's right. A daily note home might be too much, but maybe a quick phone call (3-5 mins) will work. Work out a plan that works for both of you.
Education.com also has some great resources on how to communicate with teachers. Check out -
http://www.education.com/topic/parent-teacher-communication/
Hope that helps. You are doing the right thing by getting involved now.
Barb Kruger
www.LessonPop.com