It was a 2 battalion regiment that was part of the permanent staff of the SS-Panzergrenadier Schule at Prosetschnitz/Kienschlag. It tested and demonstrated new combat tactics and weapons (for example, it extensively tested the MP44/Sturmgewehr). In March of 1944 it was sent to Hungary as part of the occupation of that country. There it was broken up to give the forming (not re-forming) 16. SS-PGD RFSS some experienced cadre, aside from the men who had been in the Sturmbrigade RFSS.
The Lehr Regiment was reformed during the spring and summer of 1944, and part of it went into SS-KG Schill in September 1944, for combat against the Slovak Rising (Schill then became the cadre for the 32. SS-FGD 30. Januar).
The Lehr Reg. was filled out again with very young ethnic-German refugees, who had fled their homes in Eastern Europe. Knight's Cross winner Vincenz Kaiser had commanded the unit through all of the events mentioned above, and in January 1945, he brought it to the Vosges front, where it was retitled into SS-PGR 38, and incorporated into the 17. SS-PGD GvB. The division was in bad shape, and all of its infantry were concentrated into SS-PGR 37, with the former Lehr Reg. becoming the new SS-PGR 38, still under Kaiser.
I don't know if yet another Lehr Reg. was formed, but the various staffs, cadres, and trainees at Kienschlag and the overall Beneschau training complex outside of Prague were formed in April 1945 into the SS-KG Division Böhmen-Mähren.