How is the Bike/Walk score calculated? Simple. Its the combined percentage of people who said they rode a bike or walked. Boom.
Want to see the math? So far, your school has recorded 0 answers to the question "How did you get to school today?".
0 said "bike" (or NaN%).
0 said "walk" (or NaN%).
0 said "roll" (or NaN%).
NaN + NaN + NaN = NaN. Round to the nearest whole number and you get 0. Now you know. You're welcome.
Keep doing more surveys. Its important. And... you get the chance to boost your score, get more accurate results, and see how your school is trending!