Bernie was looking for anything to try and prop up Castro and make Castro, and thus by extension, socialism and central planning, look good.
What next will Bernie say, that Ted Bundy was a good law student?
Secondly, Cuba was literate to a large degree before Castro and Bernie has never proven that Cuba had to have Castro to become more literate.
I like what Watters said on Fox News that basically Castro wanted more literacy to allow kids to read the socialist propaganda he sought to pup into them.