I have done a year round school schedule from the start. We take our breaks the : last week of July ( my mom takes them so dh and go on our vacation w/out the kids then) 1 week in June ( I have 1 of my nephews then) 1 week for Christmas 5 weeks total for family trips ( the time of year changes every year , mostly when KOA has a special or when the national parks are least crowded.) and some days here and there , like when family/friends come into town or we want to take a day trip somewhere. Summers are hot here also , we will be inside anyways, so why not get school work done then. My girls have to do : English/Math everyday History Monday/Wednesday/Friday Science on Tuesday/Thursday Its usually light work. Copywork, workbooks ( mad libs are great) , book reports, science experiments , logic/brain teaser puzzle books , dioramas , CD roms that have fun learning games, and other "fun" worksheets we find online.
This has been our first official year (preschool and kindergarten), but I plan to continue school through the summer. We do mostly thematic units, usually about something the boys are interested in, so I see no reason to stop that for summer. The only books my oldest has are ETC and Horizons Math (we started the K books midway through the year so will be working on those until they are done). For these younger years I like the idea of schooling year round, but being able to take days off whenever we want or need to. We just took a 10 day trip to Utah's National Parks, no book work got done, but I can't think of a better learning expeience to give my boys. The 3 year old's favorite new phrase is cryptobiotic crust, LOL.
