At numerous times, I was told by parents why their child can't come to chess class: s/he has a piano class, s/he has soccer training, s/he has a swimming lesson, we have family dinner, s/he has a birthday party, s/he has Chinese school, s/he has skate lesson, s/he needs to prepare for tests, and etc. I am not saying other things are not important, but it seems that the parents value all other things as more important than chess. What impression you have given your child? Chess is low priority, if you don't have time, you can skip it.
Then they will skip class here and there, and leave their chess education with a lot of holes. Not only they are robbed off the chance to succeed in chess, but they also learn a non-committal attitude. In future, they will use one activity as excuse to procrastinate another activity. They will not commit to anything.
As we all know, chess requires at least 5 to 10 years to reach advanced player level. If you don't have any commitment, missing class here and there, or taking one quarter of chess lesson and then skipping another quarter, or taking long summer break, the time for reaching advanced level will be doubled or tripled. Most likely, your child will drop out of chess forever.