I dont like paypal standard because it is not at all easy to set up.
setting up both PDT and IPN is not something that is easy to walk a beginner through, and here in the support forum, I encounter more people that understand IPN or PDT and have to walk them through it all together to regularly.
to best of my knowledge there isn't a sandbox for paypal standard, but apparently I'm wrong.
I would love it if you would share the information with the class so that I can be better informed