To start with, I refer you to this URL for background reading, a record of an approved school held by the National Archives at Kew, due for release into the public domain in 2029 Hereward Approved School, West Road, Bourne, Lincs: discharge register | The National Archives

Given that the vast majority of boys/youths leaving their punishment institutions under licence, left after the normal entry age range for joining the navy as a boy i.e., 15 to 16, which meant that this was not an issue for naval boys' training establishments. However, there were one or two known cases of boy's from these institutions joining as boy seamen, but of course I cannot reveal their names or recruitment dates. It did become an issue for adult entry recruits, but again, no personal details can be published. It should be noted that since approximately 1850 and contrary to what some 'romantics' may tell you, juvenile delinquents were not sent into the navy as a punishment/part punishment, but when considered to be advantageous to the juvenile's rehabilitation they were often sent to Home Office Nautical Schools, and if appropriate, applied to join the navy thereafter.

In WW2, specifically from 1943 until the end of the war, manpower was always at a premium which meant that men, who in times of peace would not have been considered for the armed forces, were welcomed with open arms.  This included men who had been in gaol, and those who had undergone corrective training in Borstals and approved schools, and I can find no record to say that they performed any less well than did the 'conventional' recruit.

When the war had been successfully prosecuted, these men once more became undesirables [persona non grata] as far as the armed services were concerned, and they were discharged and barred from re-joining. This debarring was finally made law in 1947.

My story starts with an Admiralty letter written to the Home Office [responsible for gaols, Borstal's and approved schools] on the 19th April 1948.  One of the problems at that time but by no means the only one, was the manning of the fleet. The 'clear out' of HO's [hostilities only men called-up for war service only often still in uniform as late as early 1947] coupled with the attrition rate amongst regulars and the poor signing-on, meant that morale was low, pay was poor and advancement was slow and unsure. The navy wanted more men to join and so a re-think {a RECONSIDERATION} on recruiting pre-occupied the Boardroom in the Admiralty.

1948 LETTER.pdf

This letter was used by the Home Office to set-up procedures for applicants from England and Wales.  It did not include Scotland or Northern Ireland.  It wasn't until 1953, and no doubt because of cross-office talk, that Northern Ireland decided to 'test the waters' with a view to getting some of its ex-Borstal boy's into the navy.

This next letter comes from the Stormont and is dated 10th April 1953, addressed to the Director of Naval Recruiting.

APRIL 1953 LETTER.pdf

Next, a loose minute in the File

LOOSE MINUTE 1.pdf

followed by the letter answering the April 1953 letter JUNE 1953 LETTER.pdf and the subsequent answer STORMONT JUNE 1953 LETTER.pdf

The processes above confirmed that previous 'offenders' in the English, Welsh and Northern Ireland Borstal/Approved School systems could, with the reservation shown in the correspondence, join the royal navy.  Scotland was not included.

A few months later [in September 1953], the Scots decided that they wanted to be a part of this "special recruitment opportunity and privilege." A 'canny' or perhaps a shrewd Scot, a Deputy Governor of one of H.M. Institutions north of the border, wrote to the Admiralty and posed a specific question about one of his boys  {or at least erstwhile boy}  who was an aspirant to joining the royal navy. When received in the Admiralty, whilst it did not 'fall on deaf ears', it landed on a desk of a person not au fait with the Scottish eligibility for inclusion into the newly established 'system'. 

The Deputy Governor's letter FALKIRK SEPTEMBER 1953 LETTER.pdf and the associated proverbial LOOSE MINUTE 2.pdf.

The Admiralty re-directed the Falkirk letter to the Scottish Home Department for action LETTER TO SCOTTISH HOME DEPARTMENT OF OCTOBER 1953.pdf

Finally, back came the answer from the Scottish Home Department and the last paragraph puts the case 'to bed'. SCOTTISH HOME DEPARTMENT OCTOBER 1953 LETTER.pdf

So, errant youths were allowed to join the navy from UK applicants from 1953 onwards in the same year as I joined the navy.  I joined direct from an "approved school" but mine was approved by the 1944 Education Act as a place fit for formal academic learning from age 5 to 15.  Not surprisingly, since the start of 1954 there are not that many volunteers, but, being an ex-Borstal or Approved School boy did not excuse one from doing one's National Service. The navy had relatively few National Servicemen and the 'filter' might have meant that only the best [for all purposes] got through it to be a member of the Senior Service.