TEACHING is the highest form of understanding, " said Aristotle (himself a teacher) in the 4th century BC.

"Mr Freyne it is lazy to always open your essays with a quotation, " said the late Leo Brennan, my English teacher and friend, in 1991.

Every day parents all over the country entrust their children into the care of complete strangers so that they can fill their heads with knowledge. It's quite a responsibility, so it's a good thing that a lot of them are very good at it. A special few, like Leo Brennan and Aristotle, are exceptional at it. Here's a few of the stars of the teaching world as remembered by some of their better-known pupils.

Ray D'Arcy on John Looney John Looney from Kerry wins just by being around the longest really - I had him from third to sixth class in the De La Salle primary school in Kildare. That said, he was a brilliant teacher. He went on to be the headmaster of a school down in Kerry and I believe he still lives down there.

John Looney was a man's man. He encouraged us to play Gaelic football. And we had a gymnastics team and we went on and won the primary school All Ireland, which was no great shakes, but it sounded great at the time and we all had All Ireland medals. And yet his speciality was music, although I was pretty s*** at it.

We had to do a music exam every year. And we had to sing the scales. I have an abiding memory of starting on the high do rather than the low do and by the time I got to the bit that should have been the high do only dogs could hear me. Actually, my mum gave me an envelope full of school reports from primary school. Music was always "fair". You can't really say "should try harder" in music because you either had it or you hadn't. But I didn't fall out with him over that.

Mr Looney was solid. That was the best thing. He wasn't one of those guys who went off the curriculum and preached his own thing. You just felt safe in his class and in his company. In primary school the teacher was God.

He was the centre of our universe.

And it's not an easy job. I subbed for a week in a primary school and it was a disaster. We were in an upstairs classroom and my one week of teaching ended up with a guy climbing over the banister, falling a flight of stairs and doing an impersonation of the Isle of Mann flag on the floor below. Luckily there were no bones broken. But they subsequently broke up that class. So I was instrumental in a change in educational policy.

Sinéad Desmond on Dennis Craven I WENT to the Institute of Education on Saturdays in my Leaving Cert year and there was an English teacher there called Dennis Craven who accelerated my love of English and my understanding of it beyond belief. He was great fun - full of learning but very unpretentious with it.

He had a genuine joy and passion for English that he transmitted to me. He really, really inspired me actually.

He would throw me stuff to read on the spot, things I wasn't familiar with, like Ginsberg or Kerouac, and then ask my opinion of them. It was a very good lesson to learn. It brought me to a place where I wasn't afraid to say what my opinions were. And it certainly helped me in journalism. It taught me to trust my instincts.

There was always an air of expectation before his classes. Then the door of the class would open and he'd come in and roar something out or thump the desk and everyone would be captivated from beginning to end.

There were people in that class who didn't give two figs about whether Macbeth or Hamlet even existed, but he got through to everyone.

He had massive amounts of charisma and that's something not all teachers have. He had this silvery mane of hair and he always wore tweed - the kind of English teacher that English-lovers dream of. And he had a really big booming voice and by God did it fill the classroom.

You couldn't really hide from him even if you really wanted to.

My father works in Pembrokes on Copeland St and he called the other day to say, "You'll never guess who was just in the shop. . . Dennis Craven!" and he sent me his mobile number! I don't even know if he still teaches there. I hope he does for his benefit. But mainly for everyone else's benefit.

Seán Moncrieff on Fr Joseph Cassidy I went to Garbally College in Ballinasloe in the mid- to late '70s. Fr Joseph Cassidy taught English and he taught religion. And later on he was made head of the school and after that he was made bishop, and then he was made archbishop.

I don't think I ever actually had a class with him. The main influence he had on me was that he directed plays in the school and I got to know him that way. I really loved doing those plays. About 50% of the teachers were priests but he was very unpriesty. The fact he was a priest was totally irrelevant actually. I remember having lots of conversations with him but I don't think I ever had a conversation with him about religion. He was funny and personable and very non-judgemental.

He was a very good director. He had written plays himself so he knew a lot about the technicalities of directing a play. He was very precise about everything and about making you understand how the characters felt about things, and after a while the people in the plays would refer to each other by their stage names. We were a bunch of 13-year-old method actors.

He was teaching us about life in a way that you wouldn't necessarily learn in a classroom. I remember we did a production of The Crucible, which was a very grown up play, and he somehow managed to get a 13-year-old boy to act the character of the village slut without ever using such words.

The priests lived in the school and his room was absolutely jammed with books. I have memories of being in his room doing read-throughs of plays and he'd be pulling books off the shelf all over the place and going, "Do you see that bit there?" He'd be rambling all over the place. And there were a lot of writers who he introduced to me.

I put out a book about religion late last year, and he published a book of reflections. My sister was saying that my book and his book are side by side in the bookshop in Ballinasloe. So we've come full circle.

Mary Hanafin on Sister Alice In the Presentation in Thurles there was one very good teacher called Sr Mary of the Immaculate Heart. She was affectionately known by everyone as Mol Mac, though she subsequently changed her name back to Sr Alice.

She taught both Irish and English and she was also head of the boarding school when I was boarding there.

But more than just teaching a subject, she encouraged us all that there was nothing that we couldn't do. She encouraged women into all of the professions and work.

She was always opening up our eyes to a world outside of the classroom. She had a deep love of the Irish language and was an inspirational Irish teacher and she would bring us down to the gaeltacht in Kerry so she could bring books like Peig alive for us.

She took a great interest in debating and that served me well later - the preparation of speeches, being able to think on your feet. She was almost a political mentor as well.

In fact, when I went to college, at the end of my first year I was debating whether to do my degree in Irish and history, or whether to just go on and do Celtic studies. I rang her and she said: "Mary Hanafin, you're going to go into politics so you have to understand your Irish history!" She was always taking the long view.

I think everybody in the country can remember the teacher who was nice to them, who looked after them or who did something special for them, and not just in the context of the subjects they actually taught but in actually taking a personal interest.

Sr Alice died in May 2005 and the Cathedral of Thurles was packed on the two nights - and the cathedral in Thurles is a very big cathedral. People came back from all over the country.

Joe Duffy on Michael Long Michael Long taught me for fifth and sixth class in the De Le Salle school in Ballyfermot in 1966 to 1968. Anyone who knows me knows I like to talk about Mr Long.

He used to bounce in every day. He had a shock of beautifully coiffed white hair. He always wore a suit, he always wore a waistcoat and he always wore a pocket watch - a short man, immaculately turned out every day for work. You knew he respected his job. He taught me that you dress up for work and you dress down for home.

Every Friday he'd make up the crossword based on the events of the week, put it up on the blackboard and give us the clues. He encouraged us to be interested in current affairs and what was happening around us. He told me after I had won a quiz that I was the most curious boy in the class. I only realised about 10 years later that there were two interpretations to that. Maybe I was the most curious in terms of asking questions, or maybe I was the most curious because I was odd. . .

Mr Long was well-read, well-educated, fascinated by politics and current affairs, fascinated by geography and history, fascinated by everything - and he took a big interest in us. When we were finishing up in school he got a shilling off everyone, bought a framed picture of Our Lady of Perpetual Succour and got us all to sign our names on the back of it. That was 1968 and that picture is still there hanging on that wall in that classroom upstairs.

We all loved him. Mr Long's chair was a very old captain's chair which he held together by tying string to the legs of it. One day one of the lads in the class went up and loosened the string on the chair so that when Mr Long sat on the chair it collapsed. And I still remember my hurt for him. It was only a childish prank but nobody, especially him, deserved to be humiliated in that way. I was only about 10 at the time but I could feel his humiliation.

Daithi O'Shea on Bosco �? Concubhuir Bosco �? Concubhuir taught Irish, history and religion in the CBS in Dingle and he liked everyone, whether they were brainy or not. And everyone liked him. He'd slap his own hand with the ruler and say, "Jeez. I'd hate to get a belt out of that!"

And he'd make you laugh. Nobody ever hassled him. If he put anyone out of the class they'd be the first to say that they deserved it!

He knew about everything. He'd begin talking about one thing and he'd go across seven or eight different subjects. He just had a bit of knowledge about everything and it'd just fit into place. He'd begin talking about the history of a building and suddenly he'd start to talk about the rock and where the rock had come from and how the rock had formed, and suddenly you'd be doing geography. He'd have the blackboard full of writing in different coloured chalk.

The blackboard would end up like a Monet picture.

When I went back to repeat my Leaving Cert I found myself in a different class and Bosco saw that I was a bit of a fish out of water.

He gave me a kick in the backside and made me join the debating team, which I suppose comes in very handy doing the job I'm doing at the moment. And he got me involved in a few plays and drama in school as well. He found a niche for me in a very nice way. A lot of things I have now I could attribute to him.

I was a teacher myself for about a yearand-a-half. I had great craic teaching. I'd make sure that the blackboard was full of different colours just like Bosco did. I'd have based a lot of the stuff I did on him.

I meet him now and he's just so proud that I got on well in television. He's the kind of fellow that would have been telling me I could do it years ago when I'd have thought I couldn't do it at all!