How much should be linked to behaviour?

Our 4.5 year old son started school this September and is having some challenges with behaviour there. However I am unsure how much his behaviour at school should impact our time at home.

The school are being absolutely excellent about teaching him how to behave at school, really pro-active, positive about communication with us, and really supportive to our son. Alongside normal discipline they also reward good behaviour. Currently he can earn stickers for behaving for a set part of the day, so can get 6 stickers in total. Currently 4 or above gets him a fancy sticker at the end of the day. Our son loves stickers!

If he gets 2 or below when he comes home we discuss it with him and he looses some of his Lego. If he gets a 4 or above that Lego comes back. This shows we support the school and are all on the same page. So far very clear!

However, what do we do about everything else? For example yesterday he got a 2 for the second day in a row. I removed more Lego as per our agreement, but also there was a PTA meeting that was going to be at a softplay and we didn't go as I thought that would be seen as a reward. He didn't know about it, so he doesn't know we missedit. So now I am now left feeling like his behaviour has led to me missing out on a meeting I actually wanted to attend and he learnt nothing. We have also got him a new bike, he has outgrown his current one, but not sure if we should give it to him. Again he doesn't know about the bike so not giving it to him seems to be teaching nothing but punishing us as we can't go out on a bike ride.

Any advice would be appreciated. I obviously do not want to reward bad behaviour, but I also do not want to put our lives on hold. I am just very confused!