I don't think I taught DS, he just appeared in the living room one day with an apple which had been in a sealed packet, and announced proudly "I cut the bag with scissors mummy!"
- they would have been the normal scissors just out of the cutlery drawer! I've always been cautious but non hysterical around them and he is aware that they can hurt him and he mustn't try to cut himself or touch the insides of the blades.
I gave DS proper scissors when he was 2, and supervised closely. He loves cutting up paper / catalogues, and has been accurately cutting for a while now (he's 4 next month). I think proper scissors + supervision is better than the frustration that is plastic scissors.
We got some great kids scissors with a spring part that pushed the blades apart - which really helped getting the cutting action. You could disengage the spring once no longer needed. They do have metal blades though, so need supervision.
A bit like these but not that exact brand. Or these look a bit safer, but at the price!
My DM taught DS when he was not quite 3. Admittedly she has an old school no nonsense retired teacher thing going on.
On one of her trips down south to see us, she presented him with some proper kids scissors (for older kids) - obviously with no consultation with us. The conversation went as follows:
DM: Little boy scissors don't cut properly so I've bought you some big boy scissors. If you're not careful you'll cut yourself and it will hurt and bleed a lot. So concentrate and don't do any cutting if Mammy or Daddy aren't there. Ok?
DS: Ok Grandma.
He was so bloody terrified he was indescribably careful for months! I seem to remember him using two hands for a while.
All of the finger rhymes, playing with play dough, rolling balls, drawing etc will build up the muscles needed for using scissors, it's a really tricky manoeuvre to use scissors one handed and the first stages are using two hands, there are lots of scissor styles you can buy to help with those early stages such as parent scissors ( with holes for an adult hand too), snip scissors, loop scissors and spring loaded scissors (which ones are needed is dependent on what stage your child is at) once the child is snipping then play dough is a great resource to support in developing and practising this skill but I really feel pre school should be talking you through where they feel your child is at and how you can support this development at home. Hope this is helpful