Here's some ideas of what you can look out for when practicing catching them
Make sure that you are genuine. Children can see through false compliments, exaggerations, and flattery. On the other hand, earning genuine praise makes children feel good. After giving praise, make sure your children know exactly what they did that pleased you, so they can repeat the behaviour. Be sure to tell them why you think what they did was good, and how it will benefit them and others. Finally, get your child to respond to your praise so you know he or she understands why you are pleased with a particular action or behaviour.
Behaviours to look for
coming into the classroom quickly and quietly looking at the teacher quickly and quietly when asked to listen following an instruction the first time they are asked helping a classmate being polite tidying and cleaning up working hard on a piece of work putting their hand up and waiting to be asked to speak holding the door open for someone handing homework in on time catching up with unfinished work or work missed due to absence saying ‘please’ and ‘thank you’ asking for help when they need it walking quietly around the school listening well in assembly providing a good idea or suggestion in a discussion working well with a group of classmates listening to another's point of view telling the teacher of a problem in the playground rather than trying to sort it out by fighting letting a teacher know if someone is bullying another pupil carrying out a classroom job willingly and doing it well looking after a younger pupil or a new pupil offering help without being asked taking turns; waiting for their turn treating school books and equipment carefully starting work quickly keeping own books and possessions tidy keeping own physical appearance tidy moving from one task to another without teacher reminders getting all equipment needed for a task without being told telling the truth listening quietly, looking at the speaker (‘paying attention’) lining up quickly and quietly being a good friend willing to answer questions and make contributions to group discussions remaining calm during a difficult situation sharing equipment or activity with a classmate taking a lot of care with . . . / putting a lot of thought into . . . a piece of work finding something appropriate to do when they have finished their work early speaking well in the school play or assembly being willing to try something new or difficult asking before they ‘borrow’ something remembering to do something (eg taking a message home) taking a visitor to their destination rather than just directing them bringing appropriate books and equipment to the lesson
All these are an introduction to your specific comment about you think they have done