Rules suitable for my students?

[Thargor]

Does it have to be massed ranks of hundreds of figures per side?

If not, have you considered Mortal Gods? and you could then expand to Mortal Gods:Mythic to introduce some classical mythology too.

Armies can be quite small, so tables can be too. Rules are easy to pick up and games don't take long to play.

[trev]

If this is for a one or two games with totally inexperienced players I would use Junior General or the One Hour Wargames rules.  Ideally the same set for both games.  Both are great introductions and will get everyone into the action quickly, without too much explanation being necessary.  Simple and elegant rules like these are focused on the fun and the history, which is what you want to start with.  The simplicity is a bonus with novice players as they get into the game with no lag time.  If the students show continued interest you can always switch to more complex rules later and by then they will already be familiar with many of the basic concepts.

Years ago I ran a Culloden game for some Scouts using a cut down set of rules.  Even this was too complex and I had to largely wing it as I went along on the day to keep things moving.  Discussing the plan, moving units, rolling dice, killing their mates' troops, all that was fun.  They even quite liked learning a bit about who wore red or tartan and which units were good at shooting and which were good at hand-to-hand fighting.  They especially loved winning, getting to be the king and gloating to their mates who lost afterwards.  Precise wheeling, unit formations, flank attacks, long lists of combat factors or getting run down by cavalry because you weren't in square were all ditched with no real loss.  Did they have a good nuanced understanding of 18th century warfare at the end?  No, of course not.  At best they had a very stereotypical and historically inaccurate understanding but they had fun and hopefully they learned a little bit of history.

Love to hear how it goes whatever you choose to try.

[WuZhuiQiu]

Might something like Infamy, Infamy do, albeit at more of a skirmish level?

[Olivero]

I guess my advice will be too late, but anyway here goes ;-)
Instead of OHW I would alwas prefer Wargaming: An Introduction (same author) for new players. OHW in my pov is for more experienced players who can fill in all the gaps these rules leave open.
Or try "De Re BelloLudi Ancient and Medieval rules". They were kind of written for your purpose (ok, juniorgeneral even more so, but the BelloLudi rules are "full" rules