Why did my father got mad at me and not my brother?

I'm the middle child, also the unotice child. The only time I ever get notice is when I'm in trouble, seriously. So today I got my report card, my brother use to have As back in middle school. But now we in high school his grade well pretty much got flush down the toilet. Me I continue getting my Bs and Cs. So since today's report card I got one F and one D, well my brother got all Fs. My dad didn't say anything to him, but me he came to me and start getting angry. I mean why did he gets mad at me and didn't say noth to him? That's not fair