Can my principal call meetings during my planning period?

No. Each teacher actively engaged in the instruction of children in the public schools of Texas shall have at least 450 minutes within each two-week period for instructional preparation, including parent/teacher conferences, evaluating students' work, and planning. A planning and preparation period may not be less than 45 minutes within the instructional day. During a planning and preparation period, a classroom teacher may not be required to participate in any other activity. Such a 45-minute period must be provided in its entirety (1) without regard to any other time free from supervision allotted to the teacher for other reasons, and (2) within seven hours after the commencement of classes for the school day.

Any teacher who teaches in more than one school must be provided with the required 45-minute planning/preparation period within seven hours after the commencement of classes in the school in which the teacher's first teaching assignment of the day is scheduled.

Districts which extend the school day beyond the required seven-hour minimum for instructional purposes may include the required 45-minute planning and preparation period within that extended school day. Preparation and planning periods must be scheduled within the time that students are being instructed in regularly-scheduled classes. A district may not extend the seven-hour school day solely to provide time for the required 45-minute planning and preparation period. Such extension can not be to provide time for extracurricular activities.
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Can we be assigned other duties such as watching other classes during planning time?

No. The law is clear.  However, if you are provided with more than 450 minutes for planning within a 10-day period, the time over that amount can be used by the principal for other activities.

Can we be asked to meet with parents during our planning time?

Yes. That is one of the purposes of this time. The time is also for reviewing students' homework and for YOUR planning and preparation.