Let the number of students from South Springdale High School be \( x \).
According to the problem:
- North Springdale High School is sending \( x + 5 \) students.
- West Springdale High School is sending \( (x + 5) + 6 = x + 11 \) students.
Now we can express the total number of students sent by all three schools as:
\[ x + (x + 5) + (x + 11) = 46 \]
Combining like terms:
\[ 3x + 16 = 46 \]
Now, we can isolate \( x \):
\[ 3x = 46 - 16 \] \[ 3x = 30 \] \[ x = 10 \]
Now we know:
- South Springdale High School sends \( x = 10 \) students.
- North Springdale High School sends \( x + 5 = 10 + 5 = 15 \) students.
- West Springdale High School sends \( x + 11 = 10 + 11 = 21 \) students.
Thus, the number of students coming from North Springdale High School is:
\[ \boxed{15} \]
This corresponds to option B: 15 students.