xtreg - Longitudinal dataset (5 observations) with complete treatment data bit missing observations

[Kai Hockerts]

I am not sure if this group is still active. We have a data set in which students were surveyed over four semesters resulting in five observations (t0, t1, t2, t3, t4). For each semester we have the treatment which were a natural experiment. Students from 20 study programmes received different levels of treatment (in terms of ECTS received) at different times depending on the study programme they were in. 

As can be expected we have missing data.

We plan to use fixed effects (xtreg). 

How will r deal with missing data?

Is that suction inappropriate?

How should we deal with this? 

Many thanks in advance.