Scholars disagree as to whether or not Polonius is a pretentious boor. His advice to his son, Laertes, strikes me as fairly cogent, I have to say. "Give all men they ear, few thy voice." Makes sense. What is not in dispute is that Laertes has heard it all before. Indeed, I saw a good production of Hamlet recently in which Laertes and his sister, Ophelia, were silently mouthing, "Neither a borrower or a lender me" right along with their dad.
I would argue that your kids also know every thought in your head. Indeed, if your kids weren't so bored hearing you pontificate, they could pretty much quote it for you. Your best friend may be able to finish your sentences; your kids can quote whole paragraphs.
"Study in a clean, well-lighted place without distractions, music, or smart phone, study the subject you like least first so you'll look forward to the other responsibilities and will be less likely to run out of time or energy, look at your planner to ensure that long-range deadlines don't sneak up on you..." And on and on. Excuse me while I go look for a fork to put in my ear.
In addition to your advice, your kids also know your opinion. If for example, you believe your child to be "as dumb as a dog," you can best believe that this information has been communicated--"exuded" if you will--and need hardly be articulated repeatedly. The son to whom the above was conveyed was having some trouble with reading and had to attend summer school to pass geometry. His father had been a more successful student, spoke 11 languages. His linguistic ability notwithstanding, the father could not fathom his son's lack of success in the classroom.
Speaking as someone who frequently has trouble with one language, never mind several, I am sympathetic to the struggling kid. I feel certain that the student, who grew up to be successful in other endeavors, was well acquainted with his father's assessment of his academic ability or lack thereof. I appreciate a good insult as much as the next man--Billy Wilder's, "He has Van Gogh's ear for music" is among my favorites--but leave your kids out of it.
So your kids already know your opinion of whether or not to borrow money; your kids know your impression of their school performance. So why repeatedly state the obvious? Now that you mention it, why even think it? Dogs are said to sense fear; your kids perceive unspoken disapprobation. Which do you think is more likely? "My dad thinks I'm stupid, therefore I'll study harder" or "my dad accepts me for who I am; I'm going to make him proud"? Unconditional positive regard gets my vote.
Oh, and to whom was "you are dumb as a dog" spoken? Someone who earned three primetime Emmys, two daytime Emmys, and a Golden Globe Award among other endless encomiums for hard work and talent. He performed with the greatest comics of a generation--Mary Tyler Moore and Bob Newhart. In addition to Arrested Development and Happy Days, he performed Shakespeare's Coriolanus and MacBeth.
Not bad for a kid who had to go to summer school and endure the insults of his father. Although I have to admit, I don't know if Henry Winkler, who starred in every production you can name, ever performed Hamlet.