I Remember in Boot Camp back in 1973 that there was a special ‘squad’ that was segregated and given up to six weeks of special reading and mathematics remedial lessons. If they could pass at the end of that time they could go on to regular boot camp. Of course the Viet Nam conflict was still ongoing and a body was a body back then.
That was the tail-end of project 200,000 which began around 1969-70. I went through infantry training with some of them in 1970 and I was stationed with some of them. Most were nice enough and tried, but could barely walk and talk at the same time. Most did not end up in combat arms because they could not make it through the training and nobody wanted to have their lives dependent on someone with the intellect of a stump.
The current negative press about the status of our ICBM forces partially got it's genesis there.