The Teks may be outdated on purchase, slow, unresponsive and annoying to use, but they will get the job done and won't have a lot of fuss.
Your procurement department will favor Tek because they have established distribution channels, and they know they can source replacement units as needed. Danaher aside, Tek will still be around in 5 years.
On the other hand, the Rigol scopes are dubious in their longevity, hell the most critical parts in them are overclocked and intentionally run out of spec right from the factory. And from what I've seen and my own experience, I'd deem them a poor choice for the school's use on that point alone, nevermind the fact that getting replacements is like pulling teeth, and whatever scope model they buy will guaranteed be unavailable 4 or 5 years later. If the company is still around.