No, I do not advise you parents and parents-to-be telling your kids this. This makes for highly anxious kids (albeit successful ones, in my case) and seriously, don't beat your kids over a B grade. When I think of all the other mischief I got into or could have gotten into (and other kids around me were getting into)--dude, B's were the least of my parents' worries.
I think it was around Pre-Calculus and year three of negative reinforcement by Mean Masochistic Math Tutor that I decided to jump ship and focus on what I truly excelled at, rather than feel constantly discouraged by "only above-average" grades in math and the hard sciences (alas, but for chemistry and physics I could have been a decent biologist). I actually gave up on math. Contrary to my parents intentions, all that mental/physical flogging did NOTHING to inspire me to do better in math. I grew to hate math and believe myself truly bad and stupid at it. This, I've learned, is false, because I'm quite good at college/graduate-level statistics when I apply myself. But the damage has been done, and I've never been easy about getting B grades, and getting such grades (or heaven forbid, worse) convinces me that I lack the requisite talent and intelligence for some endeavor and just want to give up on it.
Again, do not do this to your own children. Especially if you want them to go to law school.
From Orly Lobel at PrawfsBlawg, a tip off to two works on learning to cope with mediocrity, failure, and the dreaded B-:
Wendy Mogel's forthcoming book, The Blessing of a B-
Grant Norris' article Preparing Law Students for Disappointing Exam Results: Lessons from Casey at the Bat:
It is a statistical fact of life that two-thirds of the law students who enter law school will not graduate in the upper one-third of their law school class. Typically, those students are disappointed in their examination grade results and in their class standing. Nowhere does this disappointment manifest itself more than in their attitude toward their classes. In the fall semester of their first year, students are eager, excited, and willing to participate in class discussion. But after they receive their first semester grade results, many students withdraw from the learning process - they are depressed and disengaged. They suffer a significant loss of self-esteem. This article considers whether law professors should prepare their students for the disappointing results - the poor grades - that many are certain to receive. I assert that professors do indeed have a role to play - in fact, a duty to their students - to confront this problem. I offer a strategy by which professors can acknowledge students' pre-examination anxiety and deal constructively with their impending disappointment. There are lessons to be learned from Casey at the Bat, Ernest Lawrence Thayer's immortal poem about failure.
Never were truer words spoken. Law students didn't get into law school by being mediocre--they're used to excelling in school and extracurriculars, and most have had rare encounters with grades below A-. I remember my first semester I was so excited--until I got straight B's. Despite an appalling amount of work, and living at the law school from 8:30 am in the morning till 11:30 pm at night (I packed lunch and dinner, and left when the library closed, despite living only a 10 minute walk away).
First year law students are unprepared to confront these truths: that natural intelligence doesn't always determine success; that hard work is but one factor leading to success; that success is not merely measured by the highest grade; that "learning" may occur even if the grade you receive doesn't reflect it to your satisfaction. They are used to what I was used to since the age of five (when my kindergarten teacher criticized me for drawing outside of the lines, so my parents made me practice coloring for two weeks until I "got it")--B's are bad and should be beaten. And once they/I got the the B-grades (or worse!) the self-flagellation began. The feeling of demoralization, depression, the "did I choose the right career," the "I suck at this and should never have tried to do something that does not come naturally to me as breathing."
You know what? Graduate school of any kind is hard. Even if the average grade for graduate seminars is an A/A- (it's the standard grade, rather than actually reflecting the work turned in, I think, at least from what I hear from grad school friends who turn in papers last minute), graduate school is hard what with the comprehensive and qualifying exams, field tests, defenses, etc. Grades are but one part of the performance, and so even if you think you could have gotten A's in a cognate discipline rather than law school, I doubt you'd be working or stressing less.
I will say it again: graduate school was hard. You thought college was hard? It was hard compared to high school, but eventually you got "used to it," and grade inflation and the self-selecting process after those general ed requirements are done with mean that by the time students reach their senior year, they are used to being geniuses. Such is the case when you only take classes in your comfort zone, and after you've had four years to get used to the college way of writing and grading. The shock of the new for first year grad/law students is what gets them--they forgot what it is like to have to be the newbie and really try at something.
Life is hard past the age of say, 18. Hell, 21. It doesn't matter what school you are in--it will be hard. So is your first "real job." Nothing comes without a learning curve. It's just that first year law students come in thinking they've "mastered" something, and so anything difficult is unexpected. It is true that they have mastered the art of doing homework, writing predictable, formulaic essays, doing lab work, doing standardized tests. But the time to demonstrate excellence in those things is over. Now they have to deal with a new set of tasks, which are not only inherently difficult, but entirely new. Legal analysis ("thinking like a laywer") isn't rocket science, but it is it's own thing (blah blah sui generis) and new to most law students. Feeling like giving up after that first B-grade is easy to do, but first year students should resist it as much as possible.
I cried when I got my first grades. I felt like dropping out. I was all of 22 years old (I had juuuuust turned 22) and totally naive, and totally too puffed up with a sense of my own importance. If it didn't come easy and naturally, if I didn't get constant adulatory feedback, if it didn't reflect the PBK, honors-student, prize-winning student I had always known myself to be (once I dropped the 'too-hard-to-try math thing), then I thought it wasn't worth it.
This is a profoundly immature, selfish, and solipsistic attitude. Avoid this.
And avoid creating the conditions for it by preparing yourself (and your children) for the fact that the things worth pursuing in life don't always come easy. Effort is not a bad thing. Risking failure is a good thing. Trying hard and not meeting your expectations means you should keep at it, not give up. B's aren't bad, they're actually pretty good and quite common (unless you go to real graduate school, in which apparently they are bad, and the average grade is an "A"--but we're talking about law school here, so whatever).
Nothing in life is easy past a certain age, and there's some good in that. If it were too easy, you wouldn't really be trying, and you wouldn't be really living actively. Passively coasting through life is for some, but it can get rather dull to remain unchallenged and unmotivated.
So, B's aren't so bad, and don't beat your kids (or yourself) over them.