The soccer stadium sold 1,200 tickets to a match. If 3/4 of the tickets sold were adult tickets, which cost $25.50 each, how much money did the stadium make from the sale of children’s tickets if they cost 2/3 of the amount of adult tickets?

To find out how much money the stadium made from the sale of children's tickets, we first need to determine the number of adult tickets and children's tickets sold.

1. **Calculate the number of adult tickets sold:**
\[
\text{Adult tickets} = \frac{3}{4} \times \text{Total tickets} = \frac{3}{4} \times 1200 = 900
\]

2. **Calculate the number of children's tickets sold:**
\[
\text{Children's tickets} = \text{Total tickets} - \text{Adult tickets} = 1200 - 900 = 300
\]

3. **Determine the cost of children's tickets:**
The cost of children's tickets is \( \frac{2}{3} \) of the cost of adult tickets, which are $25.50 each.
\[
\text{Cost of children's tickets} = \frac{2}{3} \times 25.50
\]
Calculating this:
\[
\frac{2}{3} \times 25.50 = \frac{51.00}{3} = 17.00
\]

4. **Calculate the money made from the sale of children's tickets:**
\[
\text{Total money from children's tickets} = \text{Children's tickets} \times \text{Cost of children's tickets}
\]
\[
\text{Total money} = 300 \times 17.00 = 5100
\]

Therefore, the stadium made **$5,100** from the sale of children's tickets.