Apple’s Photos app does not allow you to perform batch processing. However, there is a way that you can quickly apply the same changes to multiple photos.
Start with any photo in edit mode; to edit a photo, select it and press Return. Photos switches to its editing interface with controls at the right side of the window. Make whatever changes you want to the photo: adjust the color, contrast, brightness, or apply a filter.
You can then switch to another photo in edit mode and paste these adjustments. To do this, choose Image > Paste Adjustments, press Command-Shift-V, or right-click on the photo and choose Paste Adjustments. Photos applies all the adjustments you made to the first photo, with the exception of cropping or rotation.
Kirk McElhearn
If I understand this correctly, you can’t actually select multiple photos and paste adjustments at once, you have to: select each individual photo, apply, repeat. To call this ‘batch processing’ is a massive overstatement. On top of that, you have to manually rotate and crop photos later.
To be fair, Microsoft’s modern Photos app doesn’t seem to be any better at this, but the older Photo Gallery (now discontinued) allowed users to select multiple photos and perform adjustments on all at once.