Why does this guy do this?

A few days ago a guy i haven't talked to in awhile randomly texted me outta the blue saying that he liked me a lot and all that jazz. He now texts me around the same time every night, but doesn't say a word to me at school. He'll glance at me and then look away. I said hi to him today, and all he said was hey all shyly and then kept walking. He also saw me in the hallway before class started this morning and then texted me telling me i looked really cute today when he could've walked up to me and just told me face to face. Why will he text me anything but won't say anything at school?