Children in teh 18th century could be educated at home,with governesses or tutors, or at small private schools, often, like that run by Mr Geroge Austen, JAs father, as well as attending public schools , like Winchester and Westminster.

The post header is Jane Austen's feeling comment about her nieces Marianne and Lizzy who were sent away to boarding school at the ages of 7 and 8 after the sudden death of their mother,Elizabeth, in a letter she wrote to Cassandra, dated October 15th , 1808.

She might have written from bitter experince, as she also attended Mrs Crawley's boarding school( in Oxford and then almsot tragically at Southmapton when aged 7, to accompany Cassandra.

Edward Gibbon was attending Westminster School aged 8 I believe.

And there is in JA's own family experience, the son of Warren Hastings, George, who lived with the Austens at Steventon when he was sent to England from India aged 7 years to be educated.:sadly he died whilst in their care( see Jane Austen: The Parson's Daughter page 9).

So yes, it is ,IMHO, pheasible that John Dashwood was sent away from Norland to be educated by a tutor or at a boarding school, after his mother's death from around the age of 7 or 8. This could explain his detachment from that part of his family.