C. F. Keil and Franz Delitzsch on Proverbs 22:15

Pro 22:15 15 Folly is bound to the heart of a child;      The rod of correction driveth it forth.

Folly, i.e., pleasure in stupid tricks, silly sport, and foolish behaviour, is the portion of children as such; their heart is as yet childish, and folly is bound up in it. Education first driveth forth this childish, foolish nature (for, as Menander says: Ὁ μὴ δαρεὶς ἄνθρωπος οὐ παιδεύεται), and if effects this when it is unindulgently severe: the שׁבט מוּסר (vid., Pro 23:13) removeth אוּלת from the heart, for it imparts intelligence and makes wise (Pro 29:15). The lxx is right in rendering 16a: ἄνοια ἐξῆπται (from ἐξάπτειν) καρδίας νέου; but the Syr. has “here mangled the lxx, and in haste has read ἀνοίᾳ ἐξίπταται: folly makes the understanding of the child fly away” (Lagarde).