It is SPOILED horse behavior. At 8 weeks he should still be getting nipped by mama for trying things. You have to step in and be mama. You cannot say 'no'. You have to say NO (I use "quit" as no rhymes with whoa).
^^Agree^^ One loud, deep QQUUIITT!! works for all of my horses big or small.
If you are doing the butt rope method make sure that he is used to the rope all over his body before pulling on him. Just like you rub the halter all over and on his face before putting it on him (I hope). Then if you are doing the drag method, thus far his only experience with a lead rope has been "step on it, get my face pulled, scary!" I personally don't like or use this method. Rub the rope allllll over his body so that he is used to feeling it around him. Once he stands still for that, then work on leading with the butt rope method. If he still rears or pulls/walks backwards go with him until he stops (SAFELY, don't get struck if he rears) and reward any of the slightest attempt to move forward (EI- drop the butt rope, pet his neck, tell him he's good) Then do it again.
The method that I use on babies and big horses goes like this:
1. Get them used to halter and lead rope (as stated above, rub all over body until it isn't scary anymore)
2. Attach lead rope and stand in front to one side about 5ft or so and pull toward you. If the horse moves, go with it when it's standing still again stand to side and pull again. Do this on both sides to teach them to give to side pressure.
3. Once the horse stands still and will turn only its head toward you when you pull, Teach the horse to disengage hindquarters. (on a baby this is more like moving around you until they face you as they lack coordination enough to cross back legs) Teach both directions.
4. After they have learned to disengage to both sides, get them moving in a disengaging circle then take a few steps backward and see if the horse will take just one (more is great) step toward you. Teach both sides.
5.When you can get just one or two steps forward (after disengaging both directions) start to disengage but walk backwards a few step. Both sides. Eventually the horse figures out, with very little pressure and little if any pulling, to follow you.
With some horses the whole process takes a day or two. Some take a week or two. Depends on the horse, as always. Just ALWAYS remember to reward the slightest try by releasing the pressure. A training key is to quit after the first few GOOD tries, then leave the horse alone in the stall, or round pen, etc..., to "think" and repeat the lesson again later (morning, evening).