He said that he was going to teach them magic, but he only taught them some basic knowledge and tossed them some spells and a simple Law of Meditation, then sent them off to train by themselves.
It was not like Benjamin was trying to slack off or anything, but it was extremely easy to be an apprentice. As long as you were able to utter a spell and cast some extremely minor magic, you are good to go. This process still mainly depended on the talents of an individual; if one was talented, he would be able to pass within the first try, otherwise it would take him a good amount of practice and training. No outside help could speed up that process.
These two was discovered by Benjamin because they were born with spiritual energy. Thus, after they were given different branches of magic to try, they did not take long to finally cast out the Flame Spell and Breeze Spell. Now, they have officially stepped into the castle of magic.
"S-Sir! I…. I’ve succeeded!"