I read 'work hard' as 'fuck hard' ...now I'm doing it, lmao. And actually on the second day he is going to show up 'late', but it'll be for a reason. He wants to see if she takes his advice seriously, and keep her prepared for his instructing methods. This time being late will have purpose, rather than 'Oh, right, I'm responsible for you guys'. The Clone Technique was an academy-level one with simple handsigns and was a beginner-level jutsu - Kakashi is defying all reasoning by jumping Sakura to a technique all the way up to B-rank with way more handsigns.  May sound simple on paper, but I think Sakura may come to discover that Kakashi encouraging repetition is going to have some serious meaning. If Sakura can manage to walk home without stumbling, I think he'll be disappointed that he didn't work her harder on her first day. Kakashi isn't playing games son xD