Isn't it any part of 5 calendar months?  I haven't had to research it in a while.

When I was in school Spring was mid-January through early-May so that would be 5 months even if it was less than 150 days.  If the semester ended in April (or started in February) then you might only have 4 months.  But I think you're probably tripping over the 5 month rule, making them qualify as a full-time student.

Without earned income greater than half of their support I think you're caught in the kiddie tax trap.

Rick

Edit: What Bill said (sorry got called away while I was writing this!)