If you have a reasonable saw and a fairly new and sharp plywood blade, I'm guessing that it is more the fault of the wood and not necessarily the saw, blade, or you.
1/8" wood can present some problems anyway but, are you sure that it is wood all the way through or do you maybe have some of that cheap stuff with foam core in it? The cheap plywood is only three layers thick and the center (thicker) layer is not wood even though to outsides look very nice. The outer skins of that cheaper "plywood" are very thin and can even be sanded through without much trouble.
I hate to say it again but, "you get what you pay for" and your quality depends on the materials used as well as your skill and finishing techniques.
Rog