I taught this to year 5 pupils, although years 4 & 6 might enjoy it too.
Make sure you're somewhere like a hall or gym, as you need lots of room.
Firstly, start off by doing the warm up, which should take about 5 - 10 minutes, depending on how naughty your class is!
To 'We go together' song, teach them the hand jive and see how quickly they can do it.
After the warm up, let them get themselves into pairs, with, if you like, a gym mat or two to that pair.
Play them the Greased Lightening track and afterwards, ask them to demonstrate some moves that might go.
Demonstrate yourself with a pupil how you could do paired work to the music.
Play the music twice and allow them to make up a dance routine. If they like, they can show it to the rest of the class.
If you have any time left, Get them in a line (single file) and try and do the following:
TRACK: We go Together
Do the hand jive (pat knees X2, clap hands X2, slicing action X2, smack fists X2, flick behind them X2) whilst standing with feet shoulder width apart and side stepping once to each side. Keep it going throughout song.
Oh, and don't be surprised if they don't stop singing Greased Lightening all day.
Our school's dance and gym kit is tshirt, shorts and pumps, like most other schools. The kids went barefoot for this lesson, and so did I, but that's up to you. Some teachers did it as a spare lesson activity in the hall, just with the kids taking their shoes and socks off.