Don't you generally get a clearer picture of what is going on at secondary because you can look at the exercise books when you fancy? At our primary they are treated with more secrecy than war-time military communications.
You wait until they get a few bad marks in a subject....that particular exercise book will be better hidden and there will be more excuses for its absence, that the painting of the fallen Madonna with the big boobies.
Thankfully we have fairly good report information here, plus I stick pins in son number one until he tells me how he is doing, plus I chauffeur him and his friends around to sport a lot, so eaves drop blatantly badly after tests etc. Actually I am really proud f how supportive they are of one another with regard to tests and homework.
In honesty, I can normally tell within a few minutes of him walking in the door if he has bombed something, or done really well....it's all in the posture! Son number two will be the same, son number three will be oblivious, so that will be the teller....I will be totally dependent on the school for info.