Here’s one way someone rewrote that passage (the nominalisations they used are highlighted):
Harry’s separation from his spellbooks was a problem because his teachers at Hogwarts gave him a lot of homework for the holidays.
(22 words; 9 word groups; 2 clauses; 1 clause connector)
Here’s another way:
Harry’s separation from his spellbooks led to difficulties doing assigned homework from his teachers at Hogwarts.
(16 words; 3 word groups—the whole second half of that sentence is one noun group; 1 clause; 0 clause connectors)
Here’s how J.K. Rowling did it in Harry Potter and the Prisoner of Azkaban:
This separation from his spellbooks had been a real problem for Harry, because his teachers at Hogwarts had given him a lot of holiday work.
(25 words; 8 word groups; 2 clauses; 1 clause connector)
What about your version? How does it compare to the non-nominalised version? We’re willing to bet that you’ll see a similar slimmed down effect, even if you only used one or two nominalisations in your response.