Can parents request an excused absence from their phone?

Yes, from the Schedule page in the Parents Portal, as long as the session is still ahead of the request cutoff the school sets (a day before the session by default). The request arrives as a request — it does not change attendance directly.

An admin approves or declines it, and the outcome is sent back to the parent. An approved excuse means the session does not deduct the student's pack, and grants a make-up right if the school has that switched on.