Fish: If it seems to be shooting high and to the right, ask another shooter to shoot the same load, and see if the POI changes. If it does, It might be something you are doing.
Even shooting over a rest, its not unusual for a right handed shooter to pull on the trigger, anticipating recoil. That will pull the group to the Right. He will also lift his head to avoid being smacked in the cheek, so the group will go high.
Here's a trick to fool your brain, and to see if you are pulling the groups to the right. When you mount that trigger finger in the trigger guard, put the side of your index finger on the inside, bottom of the trigger guard, so that just the pad of your finger will touch the end of the trigger. Keep your finger at right angles to the trigger guard, and keep the finger in contact with the guard as you squeeze the trigger. The support for your finger will help keep you from yanking on the trigger, and will release the trigger when you don't expect it to do so. That will keep you from lifting your head off the stock in anticipation of recoil.
YOu also want to make sure that your rest and rear sand bags, and bench or table is high enough so that your face is not laying down on top of the buttstock, instead of keeping your head upright, and along side the stock. Even the mild shove of a light load in a 20 ga. gun on your cheekbones will get your attention. To give your left hand and arm something to do, curl them in front of your chest, and bring the hand up to hold the butt of the gun, with the fingers between the butt and your arm or shoulder. That will also cushion the recoil to protect you from developing a flinch. Or, if you use a rabbit ear rear bag, then use your left hand to squeeze the ears together or relax them to raise and lower the gun in relation to the target. Your Right thumb should be along side the stock at the pistol grip, and not wrapped over it. Pushing down on the wrist of the stock in anticipation of recoil, but clenching your hand into a fist, will also cause your group to strike high.
Finally, breath control is essential to getting groups. When you have the gun sighted on target, take a deep breath and let 1/3 to 1/2 of the air out. This relaxes the muscles between your ribs, so that your heart beat does not instantly make your chest " bounce", and disturb your sight picture. Begin counting thousandths of a second. You want to fire the shot between 4 and 7 seconds after letting out that air. Before 4 seconds, or after 7 seconds, the disturbance of your chest wall by heart beats increases, and will throw a shot. Continue your count after the shot is fired, and during your follow through drill, which should involve bring the gunsights back down to where they were located in relation to your target when the gun fired. That way, you will learn to keep your eyes open through the shot, and will be able to tell where your shot should hit on the target. When you can call your shots, accurately, your " follow through " is working for you. YOu want to see the front sight recoil straight up, and not to one side or another. If the sight does not go straight up, adjust your seating position at the bench to put your shoulder more square to the butt of the gun.
YOu can also find yourself shooting two distinct groups with your gun, both small, but inpacting in different locations, if you don't mount the gun on the foreward rest in the same position. Mark the barrel, or stock with tape 8 inches back from the muzzle, and rest the gun at that mark for consistent performance. If you are shooting a short, half stock rifle, then you might consider resting the stock on a sand bag that is right in front of the trigger guard, and as close to the rear sight as possible. This is the equivalence of " free floating " your barrel as it allows all the barrel harmonics to occur in front of your rest.