Need advice- DS pushing DD

[LarsMal]

DS (2.5) is really getting bad about pushing DD (12 mos). I have tried taking his hands, looking him in the eye, sternly, telling him "WE DON'T PUSH". I've tried time-out, redirecting- nothing seems to be working. Is it just that he's 2.5, and this is what 2.5 year olds do?

Luckily she's pretty tough, but there are times he really hurts her. (He likes to push her down by her head a lot.)

Any suggestions or do I just need to get her a helmet and wait for the day she can push back- which won't be too long!!!

Thanks!