I noticed that my 9mth old baby has been coming home with occasional bruises from infantcare. I checked with the teacher and she got very defensive and said that she;s not sure how he got it. What do you think I should do?

This is not acceptable. Talk to the principal and if they do have a cctv, have a look at it. if they do not wish to comply you could report to the police for an investigation, but you should be ready to switch to another childcare.