The only way that economists can distinguish between normal and low-end goods is to see how consumers react to changes in income  If people's income increases and the demand for something becomes smaller, such things are low-end goods
Similarly, if people's income decreases, their demand for low-end goods will increase
The poor students in the school often eat instant noodles and often go to restaurants after they find a job after graduation. For these students, instant noodles are low-end products.