The formula for lateral surface area of a cuboid is:
\[
\text{Lateral Surface Area} = 2 \times (l \times h + b \times h)
\]
where \( l \) is length, \( b \) is breadth, and \( h \) is height.
Substitute the given values:
\[
\text{Lateral Surface Area} = 2 \times (15 \times 5 + 6 \times 5) = 2 \times (75 + 30) = 2 \times 105 = 210 \, \text{m}^2.
\]
Thus, the correct answer is 210 m\(^2\).