I wore over-trousers, jacket, boots and gloves to school. Of course, being sixth form I was able to wear the jacket and the boots all day (as normal clothing), and handed the helmet with gloves inside into the school office for the day. Trousers went in the locker. Job done.
I don't see how having crushed/damaged legs isn't a bad thing? If you fall of or get hit your legs are much more likely to get damaged than your torso, but you choose a jacket first? Some people are weird...
You wear a balaclava too!
The bottom line is the whether you are going to Scotland from Cornwall, out with your mates in the next town, or nipping to school up the road, the accidents won't wait for you to save up. If you can afford a bike and insurance then you can afford same protection - it ain't going to be great, but some is better than nothing.