School timetable in calendar app

Yes there is, but it's more time consuming than deleting the unwanted occurrences.

You can copy an event (Command & C keys) and plonk it down on another day. It will require editing into a series because Calendar will only copy the instance you have selected and not the repeating events. You will need to open the new event and fill out the relevant details such as number of occurrences or end date and so on.

You've encountered the usual problem of recurring events which have exceptions: school classes which pause during a holiday period in your case.

The only way to amend this is to put each school event (an individual class?) in the calendar set to expire on the last week of the academic year and then delete the instances of the event where it falls during a holiday period. You can safely delete single events of a recurring entry without deleting the whole series. When you click on a single event you wish to delete Calendar asks you if you wish to:

Delete Only This Event

Delete All Future Events

Cancel

You may also want to insert another recurring event for the holiday period which is not only something to look forward to but serves as a visual break in your calendar between school terms.

I'd also suggest creating a separate calendar and call it something like School or Classes and use that solely for these events.