A saying for “a bookish inexperience preaching the experienced”

expressionsidiomsphrasesproverbs

Like Preaching to the choir means to speak for or against something to people who already agree with one's opinions.

What is saying when an idealist, bookish inexperience, fresh-out-of-college employee/group of employees (like a department) is/are put on the helm (and given enough power) and they start to preach the experienced, practical, seasoned employee/group of employees (the other department) about te following:

1.) the ideal procedures and protocols that should be followed like obsession with standardization (even if these procedures are redundant to subject matters)
2.) Bring in ideas that are new and fresh for inexperienced but the organization (experienced Departments) have been tested and failed before.
3.) Bring in Over the top ideas that are simply laughable if exchanged in business circles but are given serious time of the day.

when they themselves lack experience of how the market, the industry or the world works.

Note: If you are thinking how could this be happening, this might occur in combination of nepotism, cronyism and/or in Laissez-faire or seagull management style

These inexperienced department who have power over the others departments but have zero experience with the other department's work flow, still just because they have been given power they preach the more wiser departments.

Best Answer

One classic idiom/proverbial phrase is "teach [one's] grandmother to suck eggs." Here is the entry for that phrase in Longman Dictionary of English Idioms (1979):

teach one's grandmother to suck eggs coll[oquial] to try to teach, inform, or give advice to someone who is more knowledgeable or experienced than oneself: he is always telling the director how to run the business; that's like teaching his grandmother to suck eggs {V[erb phrase]: often in Neg[ative] commands or advice, as in don't try to teach your grandmother to suck eggs}

Cambridge International Dictionary of Idioms (1998) reports that the idiom is primarily British and Australian:

teach your grandmother to suck eggs British & Australian to give advice to someone about a subject that they already know more about than you | You're teaching your grandmother to suck eggs, Ted. I've been playing this game since before you were born!

And the entry in John Ayto, Oxford Dictionary of English Idioms, third edition (2009) includes a brief note on the history of the expression:

teach your grandmother to suck eggs presume to advise a more experienced person. | The proverb you can't teach your grandmother to suck eggs has been used since the early 18th century as a caution against any attempt by the ignorant or inexperienced to instruct someone wiser or more knowledgeable.

One fairly early published occurrence of the expression appears in Simon Wagstaff [Jonathan Swift], A Complete Collection of Genteel and Ingenious Conversation, According to the Most Polite Mode and Method Now Used at Court, and in the Best Companies of England (1738):

Miss. Lord! I have torn my petticoat with your odious romping : my rents are coming in ; I'm afraid I shall fall into the ragman's hands.

Neverout. I'll mend it, Miss.

Miss. You mend it! go, teach your grannam to suck eggs.

And from Henry Fielding, The History of Tom Jones, a Foundling (1749):

'I should not have mentioned it now,' cries Partridge, 'if it had appeared so to me ; for I'm sure I scorn any wickedness as much as another ; but perhaps you know better ; and yet I might have imagined that I should not have lived so long, without being able to distinguish between fas & nefas ; but it seems we are all to live and learn. I remember my old schoolmaster, who was a prodigious great scholar, used often to say, Polly matete cry town is my daskalon ; the English of which he told us was, that a child may sometimes teach his grandmother to suck eggs. I have lived to a fine purpose truly, if I am to be taught my grammar at this time of day. ...'

Thomas Fuller, Gnomologia: Adagies and Proverbs; Wise Sentences and Witty Sayings (1732) includes "Teach your Grannum to suck Eggs" (as well as the closely related "Teach your Grannum to spin") but doesn't offer any further discussion of it. Forty years before Fuller, John Hawkins, The English School-master Compleated (1692) has an entry for "Teach your Grandam to suck Eggs." in a list of "English Proverbs Alphabetically placed." So the expression had already achieved the status of a proverb in the late seventeenth century.

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