'solid lesson' is correct and usable in written English
It is used when referring to something that was learned or taught that can be applied in a practical way. Example: The teacher gave a solid lesson in how to perform basic math equations.
The Awl used fairly serious economics — but it doesn't read like that — to explain the appearance and disappearance of the McRib sandwich, which becomes a solid lesson in arbitrage and the law of one price.
Indeed, when the chips are really down the clan rallies together, sings a goofy song and delivers a solid lesson about togetherness or understanding or some other corny value.
A teacher may present a good, solid lesson.
It's been a solid lesson in losing for me too.
It was Hitchens who once noted, of children: "It's a solid lesson in the limitations of self to realize that your heart is running around inside someone else's body".
Perhaps you need to accept that your friend did something very stupid but has learned a solid lesson and won't be doing it again.
The only solid lessons on sitar he had from me were in the summer and autumn of 1966, which he couldn't pursue as much as we both wanted.
In fact, I'd wager that Snoop could give some solid lessons to some of the top decision makers and brand masters on a global basis.
After you've bumbled around and made a few mistakes which you now consider solid lessons along the networking trail you'll find yourself developing competence in your approach.
Those are some solid lessons.
A solid first lesson, combined with approachable staff and clear signs across the mountain, mean a relative beginner can explore without risking a wrong turn into a black run or off a sheer rock face.
