Six of the wounded were in critical condition before the death early on Thursday following the shooting the previous day, officials said.
Isa Aras Mersinli, 14, opened fire on two classrooms at a middle school in the southern city of Kahramanmaras on Wednesday, killing a teacher and eight students and wounding 13 others.
The gunman, who was also killed, arrived at the school with five firearms and seven magazines belonging to his father, a retired police superintendent, who was arrested after the attack.
Wednesday's attack came a day after 16 people were wounded when a former student opened fire at a high school in nearby Sanliurfa province. The victims were mostly students. The assailant later took his own life.
As of Thursday, 20 people had been detained in connection with Tuesday's shooting in Sanliurfa.
The interior and education ministries held a joint school security meeting in the capital, Ankara, on Thursday, that was attended by both ministers and all 81 of Turkey's provincial governors, as well as police chiefs and provincial education directors.
Turkey's national police headquarters revealed the suspect's profile picture on the messaging platform WhatsApp was a photo of Elliot Rodger, a college student who killed six people in California in 2014.
The Ministry of Family and Social Services announced on Thursday it had set up a team to "provide psychosocial support" to students and their families. It also plans to conduct a comprehensive investigation of similar incidents.
Funerals were held on Thursday afternoon for each of the eight students, all aged 11, who were killed on Wednesday. Maths teacher Ayla Kara, 55, who died during the attack, also was buried on Thursday.
Cevdet Yesil, whose son Adnan Gokturk Yesil was among the victims, said he rushed to the school on Wednesday after being informed of the shooting.
"And unfortunately we searched for our child, our son, until 5pm. One way or another, our security forces found him," Yesil said.
"We went to the hospital and identified (his remains). We saw he had died."
Hundreds of educators gathered in Ankara and the city of Izmir to demand greater school security.
Until this week, school shootings were rare in Turkey. But dozens of students were arrested on Thursday over social media posts implying they might stage similar attacks.
Justice Minister Akin Gurlek announced that 67 social media users were detained over posts targeting 54 different schools.
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