The period from Easter, to when European schools get out is a "hip season" for the Camino. There are more people out there, but this is the time of year I personally like to walk. I love the flowers, growing farm crops, new baby animals, and the cleanliness and newness of everything. That is why the spring is considered a time of renewal...
Once European universities and those in North America end their semesters, usually in late May or all during June, the Camino starts to come into peak season. Traffic grows constantly and fast, until reaching peak traffic loads all during July and August. it is not just students, but also administrators, teachers and some parents, whose time rotates around the collegiate calendar.
The relative decline in traffic does not occur until the universities go back into session at the end of August or into September. This is different form country to country. But, another factor is that. as a general rule, most Europeans have longer vacations / holidays than those of us form North America. So, and as many folks like to take time off work in July or August, these people contribute further to the surge in traffic. This is just an observation based on fact. It is neither good nor bad. It is what it is.
I have noticed an uptick in the number of formal student groups on the Camino during May, at the end of the student year. These groups are usually comprised of students in a Spanish or Western Civilization course that includes a week or more on the Camino as part of their course. They are usually accompanied by one or more faculty members or adult "chaperones."
The significance of these groups, and of all other organized groups, is the affect they have on reserving space at private albergues and hostal or hotels along the Camino. Organized groups tend not to stay in public albergues. They prefer private lodging wherever possible.
If you are ahead of such a group or behind one, you are lucky. It is a lot like surfing. You need to be flexible to "catch the right wave" or the though between the waves.
I always recommend being flexible. If you find yourself close to such a group, try to find out where they will be each night, and be somewhere else...
However, if your stages match theirs, private housing may be difficult to find in some places, on some routes. Just be advised. This is becoming part of managing the major Camino routes from Easter through mid-October.
If you do not care where you have to sleep for the night, great! Go in peace! However, if you have special needs, or standards, like me, this is a significant factor that needs to be managed as far in advance as possible, so it does not adversely affect my Camino experience each year.
I hope this helps.