Gregor Mendel, the father of modern genetics, failed his test to become a science teacher.
Mendel’s abbot at the monastery arranged for Mendel to attend the University of Vienna to get a teaching diploma. However, Mendel did not perform well. He was nervous and the University did not consider him a clever student. Mendel’s examiner failed him with the comments, “He lacks insight and the requisite clarity of knowledge”. This must have been devastating to the young Mendel, who in 1853 had to return to the monastery as a failure. Particularly as this was a teaching order.