A teenager used his mobile phone to record upskirt videos of at least two teachers in his school and a clip of his sister's friend while she was taking a shower in his flat.

The 17-year-old youth, who cannot be named due to a gag order to protect his victims' identities, was sentenced to two years' probation yesterday. He is also prohibited from using electronic devices with a camera and Internet functions unless assessed suitable by a probation officer or psychologist.

As part of his probation, the teenager, who will start working as a packer for a logistics firm today, must remain indoors from 10pm to 6am every day and perform 200 hours of community service. His mother was bonded for $5,000 to ensure his good behaviour.

In sentencing, District Judge Eddy Tham warned the teenager that this was his "final chance" and his probation could be revoked if he breaches the conditions. He could then be ordered to undergo reformative training instead, which would see him detained in a centre with a strict regimen that includes foot drills and counselling.

The teenager pleaded guilty on May 8 to three counts of insulting a woman's modesty, as well as one count each of criminal intimidation and being in possession of obscene videos.

On Feb 12 and 22 last year, he placed his mobile phone - with the camera lens facing upwards - on top of his bag which was on the floor in his classroom.

During maths lessons on those two days, he asked for his teacher's help and recorded four upskirt videos of the 47-year-old woman.

Using a similar method the following month, he recorded four upskirt videos of his Chinese language teacher, also 47, in the school in eastern Singapore.

Deputy Public Prosecutor Genevieve Pang told the court that the teenager also used his phone to record a video of his sister's friend while she was taking a shower in his home on Aug 10 last year.

He was caught 15 days later after police officers spotted him with a group of youngsters behaving suspiciously at the void deck of a Sengkang block of flats at around 4.30am. The officers conducted a search and arrested him when they found obscene material, including the teachers' upskirt videos, on his mobile phone.

Yesterday, defence lawyer Rajan Supramaniam said his client was extremely remorseful. He also assured the court that the teenager has strong family support.