What is happening here?
In Grade 4 your child learns to divide big numbers in columns, for example 5,376 ÷ 8. The method always follows the same rhythm: divide one digit at a time, multiply the answer back by the divisor, subtract from what is left and bring down the next digit.
It looks long at first, but it is nothing more than the times tables, one place at a time. Anyone who knows the small times tables well already has the hardest part in their head.
What helps at home
Use squared paper and write every digit in its own square. Most mistakes happen because the digits drift and the places no longer line up.
Have your child estimate before calculating: 7,912 ÷ 38 is about 8,000 ÷ 40, so roughly 200. The answer must be somewhere near that, otherwise something is off. Then do the check: answer times divisor plus remainder must give the starting number again. The check is the inverse operation, and it lets your child be sure without asking you whether the answer is right.
What can go wrong
The most common trap is zeros in the answer. With 4,056 ÷ 8 the 40 divides exactly (5), then the 8 does not fit into the 5 of the next place. A 0 belongs there (507). Children like to leave this zero out and write 57. The estimate helps again: 4,000 ÷ 8 is 500, not 50.
With two-digit divisors the question "How often does 38 fit into 79?" is hard. Then it helps to round the 38 to 40 and check the answer afterwards with the real number. Do not worry if the first try is too big or too small: that is part of the method.