Replying to Are professors allowed to lower test scores??

I'm in summer school at Colorado State U and went to my professor about the first test because I thought a couple of my answers marked wrong were actually right. Turns out they are not and he finds one he accidentally marked right that was wrong so he marks me off for it. I've never heard of a teacher marking down on a test after the fact for their own mistake. I've only experienced where talking to your teacher about a test increases your score. Is this academically ok?