It depends on your reasons.

If there is not enough room to sit, which happens during crowded masses, I see no problem with it. I also see no problem with it for reasons of health or care of small children.
I have had to stand at the back during masses because my back pain had gotten so intense I simply could not sit. I did receive some stares from the priest. But it was either that or I not attend mass that day. I would hope with all my heart that the priest would favor attendance.
Same with parents that have small children. To me it is far less disturbing that they stand in the back and comfort their children than to hear the child screaming throughout the rest of mass. I would think he would too.
It may be helpful if these persons talked to the priest to explain why they are having to stand so that he doesn’t think they are being stubborn or rude. Also, make certain they are standing in the back. Standing to the side can cause added distraction.