Halacha:

Tefillah 

Machshava:

Tefillah 

Description

We want children to act like children. Thus, when they are TOO young to understand what davening and shul are, they shouldn't be brought into the synagouge as: 1) They can naturally denegrade its sanctity 2) They can mix up other daveners 3) Perhaps will continue acting that way when older. But at the right age and time, they SHOULD and shuls should encourge.