Is responders suit change after 1NT rebid by opener forcing? (System: simplified SAYC)
This link outlines the system behind SAYC in fairly simple terms. The bottom of page 7 notes that on the auction of interest, responder must reverse or jump shift to create a game force. However, a simple new suit bid should be treated as a one-round force, 10+, game invitational. 

Most established partnerships now play some form of either Check Back Stayman (CBS) or New Minor Forcing (NMF). Both of these are predicated on the requirement that Opener's 1NT rebid categorically denied 4-card support for Responder's major suit response.

If partner rebid 1NT over your 1H response with 4-card Heart support, rightly take that as a gross insult to your card-play. Find a new partner promptly , before this one ruins your bidding.