Sally's Spinach Salad

1 1/2 bags baby spinach
1 head lettuce
3/4 c. mushrooms
3/4 c swiss cheese
1 pkg cooked bacon

Dressing:
3/4 c. sugar
1 tsp dry mustard
1 tsp. salt
1 c. veg. oil
1/3 c. vinegar
1/2 Tbsp. poppy seeds