is it standard practice

[LittleMarshmallow]

during a lumpectomy for breast cancer (stage 1) to remove lymph nodes as well?

The place that breast cancer spreads to is first to the lymph nodes under the arms. So taking some of the lynph nodes out to look at them under a microscope for signs of cancer, will give the doctor an idea if the cancer is just in the breast or if it has gone further.

Even if it has gone further, it depends on the type of cancer as to how agressive it is.

You can only "stage" a breast cancer once you know this information as part of the whole picture.
Hope all goes well