I think you may have left out a word or two in the last statement. Are you saying your P told the classroom teachers that it was OK to trade the planning periods?
I've heard of P's asking teachers to cover another class
during their planning time to avoid hiring a sub for the day. In fact, I've done that several times myself, both as a regular teacher and as a sub. But I've NEVER had a P ask me to give up MY planning time so another teacher could have theirs. That's just not right.
You may need to remind the P that you ALSO have state standards that have to be met through your curriculum and you have to document how the kids are meeting those standards. So you have to plan activities and document the results, just like the rest of the teachers.