if you are at all worried about health and safety issues in a school, you could write to the board of governors voices your worries. If you feel that you don't want to do that, you could also phone the council and ask for the education dept for your area (LEA) and talk to someone there who could look into it.
It may seem like sticky beakedness, but frankly, how many times in our news do we hear of people failed because noone stood up and said anything. It maybe nothing, or a one off incident, but if it is a symptom of a general poor standard, then it needs to be voiced. That is how a community should function, and sadly, these days people tend to be too afraid or too busy to say anything.
You could look up the name of the school on the DfEE website and read the OfSted report. THis will tell you at what standard the school is generally performing at. It might help to paint a clearer picture.
If you are really worried about the school and it is something on your heart, then you could also phone them and make an appointment to see the head. Or you could apply for a position (if you have time) as a dinner lady/teacher's helper etc and then you would really get to know the school and be doing a worthwhile task also.