OP, I'm not sure why you don't think IB/OOB don't apply to PK3/PK4--although they are not mandatory grades and you have to lottery in, they are still distinctions, and IB students have more rights than OOB students with respect to unexcused absences.
Here is the absence policy for the DCPS parent handbook:
"Attendance
Regular school attendance is required by DC law for children ages 5 to 18. Although not required by law, it is just as important for children ages 3 and 4 to have regular attendance as well. Attending school every day and on-time is critically important and has a huge impact on learning from kindergarten through high school. Even as children grow older and become more independent, families play a key role in making sure regular attendance is a priority.
Some absences are unavoidable but when a student misses too much school—excused or unexcused—they
can fall behind academically. Students are much less likely to succeed when they are chronically absent and/or miss 18 or more days in a school year. Students who miss more than 20% of their scheduled periods in a school day will, by law, be considered absent for the entire day.
If your child received a seat through the out-of-boundary lottery and has 10 unexcused absences or 20 unexcused tardies, they may be asked to return to their neighborhood school at the end of the school year."
See
http://dcps.dc.gov/DCPS/Files/downloads/COMMUNITY/Parents/DCPS%20Parent%20HandbookEnglishweb.pdf