Guard and Reserve GI Bill Parity Act of 2020 This bill expands eligibility for Post-9/11 GI Bill educational assistance. Specifically, the bill adjusts the type of service that entitles a member of the Armed Forces, reserves, or National Guard to such assistance. Under the bill, service by a reservist or National Guard member that is entitled to pay counts toward benefit eligibility. Such service includes training, active military service, inactive training, and general duty for which basic pay is warranted.