Seems more likely that the foot of clay soil is what's making your new lawn not very healthy. Clay without organic matter mixed in is not great for growing anything. It holds water and doesn't allow the water to sink into the ground, meaning the roots on plants and lawn are shallow.

The old lawn is buried too deep below to matter. But even if it were not, it would probably contain good organic material for growing. In fact, some people turn over their lawn and just leave it in place for purposes of planting a garden, hedges, whatever.

(If I understand what you said correctly you now have your old lawn buried under 1 foot of soil on top of which you've planted new lawn.)

If you really have a foot of new soil over your old lawn, you in effect have a new lawn. Very likely the new soil is different than the underlying soil. You probably need to get a soil yest and see what amendments may be called for. What kind of grass seed did you put down on the new soil.

The old grass won't cause any problems - its just organic matter, which is good.

Capt Tom

Your neighbor doesn't know what he is talking about...

yes heimert that is correct we have about a foot of soil over the old lawn and I know clay isnt the best but thats what we have to work with in this area. and I thank you for your comments

Captntom and joeypy I thank you also... while I was worried about the lawn .. the neighbor seemed to take such delight in saying that our lawn would get some wierd fungus (I had visions of it sliding off onto the street on some moldy layer of goo) Im even happier that I now know she is truely full of it.