I don't mean to call anyone in particular out. Or hurt any feelings. This is tailored towards Elementary aged students, but can be tweaked depending on the grade.
If your child enjoys going to school and seems happy, then things are great. Just stay informed about their feelings towards school and their day to day.
You never want to dismiss your child not wanting to go to school. Talk to them and try to find out the problem. Get your child to open up about what is making them feel like school isn't fun, because it should be. It isn't fun and games, but structured learning, where your child feels welcomed to participate and enthusiastic to learn. Lacking those can put a child behind.
Of course, not all problems with children are that serious. It could also be that they miss you and would rather be with you. If so, hype up school and their teacher. A teacher will never replace a parent or guardian in their lives, it's OK for children to really care for their teachers. Teachers try to foster a sense of community in their classroom and work towards everyone enjoying each others company. It's part of what makes a good classroom work. I digress. Perhaps they just need to go to sleep earlier to feel more rested and less grumpy.
But, It could be a student issue, a playground issue, a food issue (they may dislike the food), or the teacher. I am not saying to give a child full reign and allow them to stay home, but I would investigate the situation. My first instinct is to write a note to the teacher. I recently wrote one regarding issues during recess time. Things seem to be going much better now. And the changes were almost immediate. If you would rather speak to someone, visit the school, morning can be hectic, so scheduling a visit by calling the office isn't a bad idea. Perhaps arrange a classroom visit so you can silently observe what is happening during lessons or during recess time.
These are just my ideas and classroom expectations.
Take care,
Kat