53
Take the Near Impossible Literacy Test Louisiana Used to Suppress Black Votes
(www.openculture.com)
I think the answer key didn't exist. You could argue syntax on each question, no matter how it was answered. "It says draw A line through both numbers, and you did two lines total." Or "you drew one long squiggle, that's not a straight line. You should've known to draw two".
Three questions per minute, I can imagine why it was nearly impossible to finish, let alone get a technically perfect score.
And you know this was only administered as a formality to anyone too dark to be "white".