Apple Watch 4 rapid battery drain when out of range of iPhone

We recently bought an Apple Watch Series 4 GPS + Cellular for my daughter. We bought the cellular version under the impression that she could wear it to school and not have to take her phone with her. However, we discovered on her first day wearing it that when the watch is out of range of the phone the battery only lasts for about 4 hours before it is depleted enough to go into low power mode.

We did some troubleshooting by having her put the watch into airplane mode the next day and the battery drain was nominal despite her phone being at home. The third day, she took her phone to school with her and the battery drain was again nominal. We have concluded that, despite having cellular capabilities, the watch is exhausting it's battery searching for the phone and this has proven rather disappointing considering we paid nearly $700 for the watch and Apple Care and are paying an extra $10/mo with our carrier for the device.

In comparison, my Series 3 watch only needs charging every other day, but it's always within range of my phone (one of the reasons I didn't get the cellular version).

Apple Support seemed rather perplexed by this when we called, so I thought I'd try the forums to see if others had experienced this as well and if there was any solution (aside from airplane mode, which completely defeats the purpose of having cellular) that we might try. We knew you needed an iPhone in order to have the watch, but nowhere is it clearly stated that the watch must be in range of the phone at all times to preserve battery life. Employees at the Apple store where we purchased the watch did not warn us even when we told them that we were buying the cellular watch with the express purpose of allowing our daughter to leave the phone at home - they thought it was a great idea.

Little frustrated by all of this. Maybe Apple could include a feature to tell the watch to stop hunting for the phone after a certain period of time, or have a toggle for "standalone mode" to preserve battery life when out of range of the phone, especially on the cellular models.