I have used a couple of kits, and it will depend on what is most cost effective for your location. For large numbers of samples I have had very good yields and quality from Macherey-Nagel's Nucleomag 96 well plate kit, using Qiashredder columns (they can be ordered in bulk) from Qiagen as a primary clarification step after grinding and addition of lysis buffer. This combination gives good yields from leaf tissue (>100 ng/uL at 150 uL). Of course that is leaf tissue, Qiagen mini plant kits do well for lower yield samples, with elution volumes of 30-50 uL (50-120 ng/uL in my experience). Both these kits give good quality too, but the Qiagen kit requires the additional purchase of their RNase-free DNase kit for efficient on column gDNA digestion. Our lab has a different kit, from different companies for every tissue type we have (it gets to be a bit much). My suggestion is that you sweet talk some companies into sending free samples so you can test cost free for the one that works best.

i used that from zymo research (ZR Tissue & Insect RNA MicroPrep™) and It works fine with the most of difficult tissues and gives observed quality of RNA with great yeild

i hope it will work with you too