Our school district (or possibly our state) is also very strict about total # of absences and calling CPS.

FWIW, the principal's reason is sounding a lot like what happened with friends or our family who were part-time homeschooling in elementary - the school really didn't *want* them part-time homeschooling, and eventually pressured them into having to either enroll full-time or withdraw and homeschool full-time. When the school was putting pressure on the family to make their decision, they used reasons such as this - not being available to fully participate socially (from the school's point of view). Perhaps the principal's only concern is floodgates opening with lots of other parents opting their kids out of field trips, but I'm wary that there might be something more behind it in terms of finding excuses for why part-time homeschooling doesn't work. If you're *not* getting that vibe and the school is completely behind your decision and happy with it, then totally ignore this reply!

Best wishes,

polarbear