Notating Percussion For Young Players

Hello one and all.

I recently had a school I worked at ask me to write a piece for their middle school band.  I'll be honest and confess it has been a very very long time since I reviewed percussion notation (I've been teaching LA not music) and was wondering if anyone had any advice about writing percussion lines for beginners?  The students I am writing for will only have been playing for about 1-2 years.  I emailed the band director to see how many percussionists she will have for the coming school year but as of yet haven't gotten any information back.  My guess is about 6 based on last year's numbers and unless they practiced A LOT over the summer they play about as well as you would expect kids with 2 years of experience to play.    

I know more complex pieces have multiple instruments per page so individuals assigned more than one instrument can function better but I wanted to know are there any special notation standards for beginners?  Are there instruments, rhythms, or techniques that I should be avoiding?  I don't want to be torturing these poor kids to the point they want to quit nor do I want to give them parts riddled with mistakes.  I would also like for there to be some educational value to what I am asking them to do, but as a cellist I don't really know what the standard progression of 'difficult stuff' for percussionists should be.

So basically, any and all advice on beginner percussionists would be most welcome.  Thanks in advance to everyone! 

I was once asked to write a piece for a middle school, back in high school. Unfortunately, they didn't know 3/8 so it was too difficult for them. Hahaha.

In terms of time signature I had already planned on keeping it to 2/4, 3/4, 4/4.  Mostly I was asking if anyone had a baseline for what is appropriate for middle level players?  Like you wouldn't ask a middle school cellist to play in thumb position but they should be able to play in 1st position on all strings.  I was looking for an equivalent of the cello example for percussion.