Ultimately, fulfilling the basic legal requirement of attending school every day at an age where its actually on your parents to ensure you get there and any absence would be seen as their responsibility, is not an achievement.
If you've got a child who school refuses who does a whole term, by all means reward. That's an achievement.
If you've got a child with a chronic condition who has appropriately worked to come into school more often when they're borderline unwell, by all means reward. That's an achievement.
General kid with no issues doing the legal minimum every day. Not an achievement.