If you send a student solo He/She (PC or what?) is flying P1 so you can't log the hours but, If you are a FI(R) you need to record this on form from the CAA as a supervised solo flight and get your FI to counter sign the form. However do not fall into the trap of solo cross country flights. 1 solo cross country sorte is one supervised flight no matter how many airports the student lands at. Best of luck.