All you need to do is take a compass with you. Each time you change direction take a rough bearing of what direction you're going, and count your steps, writing down this information (assuming that you walk to School)
Once you complete the trip, calculate the distance based on the length of your stride, set it to a scale, and draw the map fitting the distances and directions you observed. Then include any landmarks along the way.
If you take a bus or carpool, use the compass to record the directions you go, then have someone drive the same route, and use the car odometer to measure distances.
Once you've drawn the route, add in landmarks like parks, stores, RR Crossings etc. in the appropriate locations.