Any parent let their children being take care by their grandma/grandpa?
People say afraid if the children learn the bad behavior in school, what if they learn from the old folks at home instead?

I have 2 kids whom taking by my mom. When they behave good, all is good.
But when is not, eg kids fighting over things or when both want to win over stuff...or they play till very high....they create loud noise and sometimes like creating sound pollution. My mom will get mad and then start to scold and sometimes if this happen when she's busy cooking or doing house core...she will throw temper....sometimes will cane them if situation is out of control....

So my kids little by little learn those from the old folks and treat it back to their parents. The most affected ones is my younger son who is 3y+ and recently my daughter too.

I have the plan to let them stay for full day in pre school. Coz now they only half day.

Is my move right or wrong? Any experience parents come across this problem?