I am sorry that you have had to deal with this situation, but I have found that this is fairly common in primary schools these days! Sad but true! The teachers IMO should have contacted you a long time ago for a meeting with you and brought this situation up, it would have made it so much easier for you now! I find it extremely frustrating that as parents they are now expecting us to pick up a lot of slack in the education system. So basically we are becoming teachers for our own children. I, myself, have been doing this for my DD since prep, and although I don't teach the way they do, my DD still learns what she needs to. I try to make things fun for her and not so much a lesson, I get her to write shopping lists, recipes, anything really, so she learns that way. Maths, when we go shopping, she gets to look for the cheapest of a certain item, so she is learning that way as well. I also get her to double quantities for recipes, which gives her fractions. It's more interesting than just straight maths! There are also some free computer programs for Maths on the computer, cant remember what they are called, but they might be useful too!
Good Luck!