This is the website where you can search for preschools in the neighbourhood you're moving into - as soon as you know
This is a leaflet in English:http://www.berlin.de/imperia/md/cont...o_englisch.pdf
Looks very comprehensive to me.
If the link does not work, click on "Elterninfo English" on this website, which tells you everything you never wanted to know about preschools/daycare in Berlin:http://www.berlin.de/sen/familie/kindertagesbetreuung/
I gather that any child 3 and up is entitled to a half-day place, in the disctrict or a neighbouring district, with 30 minutes travel time on public transport considered a reasonable distance. Interestingly, I read Berlin is planning to scrap fees entirely by 2011. They may not be able to keep it up though, as Berlin is so broke. Even so, fees are so heavily subsidized it shouldn't be much of an issue. I'd expect most Waldorf and Montessori schools (schools on the Sudbury/democratic model are extremely rare in Germany, not sure whether there would be any in Berlin) to be run on the public model, ie subsidized/free by 2011. The exception to this would be preschools affiliated to international schools, which may be insanely expensive, but tuition for expatriates' children is usually covered by employers, so check with whoever is employing you or your husband in Germany if you're interested.
Though pre-school is universal, it is not mandatory (not even the K year, called "Vorschule", usually a pull-out program in preschool, though this is being considered too) and it is entirely up to you whether you go public, private, or not at all.
this is the schools' website:http://www.berlin.de/sen/bildung/index.html
Apparently there is no leaflet in english, sorry, but you do read some German you say - enjoy!
Your son will probably be eligible for 1st grade in elementary school in the fall of the year he turns six. From what I know of Berlin (I live in the South) it's usually a 1st/2nd split grade, with the option of remaining for three years in that class without its being considered "holding back". Unlike pre-school, by 1st grade brick-and-mortar school attendance is mandatory! From what I know, permission to homeschool is extremely hard to get if you are legally resident - I have heard of exceptions being made if the child would have been in school for less than a year or so until leaving again, but i wouldn't count on it.
Private schools (again with the exception of international schools) are heavily subsidized to be affordable (in theory) for everyone, so schools can't cherrypick by parental income. Again, you'll find a lot of Waldorf, some Montessori, and of course Catholic and some Protestant schools. Haven't heard of Sudbury schools in Berlin (there is one founded by the singer Nena in Hamburg, with bad reviews).
From what I understand, you have to register with the elementary you#re zoned for, then opt out if you want to go private.
I hope this'll keep you going for a while. I'm happy to help with any other questions you may have on Germany - just keep in mind I've never lived in Berlin...