This is a very common problem that effects lots of people in school, everyones hormones are racing and heaps of crushes develop. You just have to be able to manage you life when that happens. Getting an education is really important, so if you find yourself getting distracted, try taking a sip of water and telling yourself to focus. You can think of this boy when you're at home, but at school it's time to learn.
With the whole spying thing, while I've never particularly understood why people felt the need to spy on their crush, I don't think you're a coward for doing so. I'm also a really shy person so I know that it's scary to ask people out and all that, but really, what is spying going to accomplish? I had a few friends that loved to spy on their crush, but they got too out of hand and they boy ended up being scared of them. So, I think the spying needs to stop, you don't want to come across as creepy when you're actually just shy.
Just try talking to this boy, if you eventually want to go out with him then you'll have to talk and be comfortable around each other. Find your common interests and flirt a little; lots of eye contact, gently touching his arm when talking, teasing him etc. You might find out that he likes you too if he responds well to this, and then you might feel better about asking him out, or he might end up asking you out! But if you really don't feel confident in asking him out, just think; if you don't ask him out, then you'll never know what could have happened and you'll have to question yourself for the rest of your life. If you do, the worst thing that could happen is that he says no, and you're sad for a while, but you can move on and learn from the experience and you don't have to ask "what if?" your whole life.
I hope this helps, sorry we took a while to reply to you! Good luck with your problem! If you need any more help or I've made something unclear, please feel free to message me!