J.G.
You can find more information on the Troy public school preschool programs at: http://www.troyceonline.com/preschool.html
They have 3 different programs that range from part-time, to full-time with extended care. I have heard very good things about all of them (PALS, TOTS, and Building Blocks). My 3 year old twin boys are signed-up to start TOTS at Niles this year. I believe there are still openings this year.
You can poke around the website and call to find out more information. Please feel free to send me a personnal message if I can help. I spent a great deal of time looking at preschools in the Troy area recently!
Also, if you look on this page of their website, there are some parent handbooks for the programs - which have more detail on the programs themselves:
http://register.troyceonline.com/CARE_DownloadForms.aspx
Others have also mentioned the Troy co-op preschool. I have also heard good things about that program, but did not look into it or visit myself.