Bluetooth Low Energy (BLE) is widely considered for wireless Indoor Localization Systems (ILS) in which BLE Received Signal Strength (RSS) is used to derive the location of the target. The efficacy of a BLE based ILS depends on the localization accuracy. Whereas, localization accuracy depends on the stability of the BLE RSS. A number of researchers have focused on studying the impact of different parameters (such as different type of devices, environments and deployments) that cause the variations in BLE RSS. Today, BLE devices are capable of operating at multiple transmission power levels. Unlike previous studies, this paper focuses on evaluating the performance of BLE based ILS at multiple transmission power levels. Furthermore, the impact of different parameters such as multiple advertising interval, scanning interval, device orientation, distance, the effect of Line of Sight (LOS), Non-Line of Sight (NLOS) and device density over BLE RSS is also studied with multiple transmission power levels. Our main findings show that multiple transmission power level can attain localization accuracy with multiple precisions (i.e. from 2m to 5m) in an indoor classroom environment.