My 17mo has started to try to kick/swipe other children who come into his space. I managed to intervene and stop It from happening but I'm mortified about it, he's very strong and chunky. I've been very clear with him that this is wrong, saying "no! Naughty! You do NOT do that." Is this a 'normal' part of development or should I be concerned? Does anyone have any advice? Im going to speak to his nursery and make them aware and ask that they're very firm with him about this too. Thank you.