There were a few words and phrases there which you can use when talking about students, teachers and classes.
oileanach (m)
student
àireamh (f)
number
cùrsa (f/m)
course
clas (m)
class
àite-suidhe (m)
seat
tòrr (m)
heap, a large quantity
barrachd (f)
an additional amount, more
meud (m)
size, amount
tidsear (f/m)
teacher
tuilleadh (m)
an additional amount, more
mòran (m)
many, a great amount, a lot
Let’s look at that list again in context.
Tha tòrr oileanach anns a’ chlas seo …
There are a lot of students in this class …
A bheil àireamh nan oileanach air a dhol suas gu mòr?
Has the number of (the) students increased a lot?
Tha barrachd chùrsaichean ùra ann am-bliadhna.
There are more new courses this year.
… tha àireamh nan clasaichean air a dhol am meud.
… the number of (the) classes has increased.
… chan fhaigh mi àite-suidhe leam fhèin ann an seòmar nan tidsearan!
… I can’t (even) get a seat to myself in the staffroom (‘room of the teachers’)!
And although we’ve seen and heard tòrr oileanach above, it’s also possible to have tòrr oileanaich.