Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Communication Breakdown
Deviation - Speed All Types; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Returned To Clearance
Procedure; Company Policy; Environment - Non Weather Related; Human Factors
First Officer was flying and distracted.  While reviewing approach plate; I looked up to see that the First Officer was rapidly descending for 6;000 feet; and was already at approximately 9;000 feet and still at 300 knots.  I immediately instructed the First Officer to turn off the autopilot; and immediately slow the aircraft to 250 knots by raising the nose of the aircraft.  Once the aircraft slowed to 250; the First Officer continued the descent.First Officer is extremely inexperienced in jets; and due to COVID-19; has extreme lack of proficiency.  Making sure new pilots in new aircraft receive more training in this time when flying becomes very infrequent.
Captain reported experiencing a speed deviation below 10;000 feet and stated First Officer's lack of flying contributed to the event.