Do not be deceived:
"Bad company corrupts good morals."
1 Corinthians 15:33 HCSB    
The righteous should choose his friends carefully,
For the way of the wicked leads them astray.
Proverbs 12:26 NKJV
He that walketh with wise men shall be wise:
but a companion of fools shall be destroyed.
Proverbs 13:20 KJV
The faithful, faith-filled, passionate prayer
of a righteous mother (or father)
can direct the course of a child's destiny (James 5:16).
So let's pray! Here's a list of items and activities we can associate with prayer for our children and their friends. It's important to remember that books, television, music, games, and other pastimes and entertainment are also very influential companions.    
When setting an alarm or when one goes off,
Father, speak to our children and their friends day and night,
even in their sleep.
May they awaken with a fresh sense of prophetic destiny,
and spend the moments of their lives
with a profound sense of urgency to reach those who are lost,
seeking to fulfill The Great Commission.
While pouring any beverage,
May they not be drunk with wine, but rather filled
with Holy Spirit of God (Eph. 5:17).
As a thirsty deer desperately pants for water,
so may their souls long after You, O God (Ps. 42:1).
When beginning Bible study each morning,
May they always, breath by breath,
enjoy a passion for You, Your Word, Your Will, Your Wisdom,
Your World (the lost), and holiness...
May they have absolutely nothing to do with the occult - books, movies, parties, activities (Lev. 20:6, Deut. 18:10-11, Matt. 12:43-45, Gal. 5:19).
May they not repeat any matter that would hurt another Christian, serve to separate them from the body of Christ, or restrict their ministry potential - uniting with the enemy to keep holy seed from being planted (James 1:26, Ex. 20:16, Prov. 17:9). 
May they be passionate about and be faithful to attend a God-honoring, life-giving church and Christian related activities, especially as they recognize The Day rapidly approaching (Heb. 10:25). Grant them a passion for involvement and leadership in small groups. May they be generous in their time in serving their church while taking their light into the world to search out and rescue those walking in darkness.
Read through class annuals, reading names aloud.
Daily pray for your children's classmates, teachers, and all in authority over them... Ask God to expose any darkness you need to be aware of that may cause your children to stumble or fall away from Him, and to break every unholy alliance... Pray that your children and their friends never compromise their beliefs, and that they serve as salt and light, boldly declaring the Truth in love at all times...
I remember Kristina walking into the house from school in tears. While on the bus, a friend had said very cruel things to her. After she calmed down, I urged her to call the girl and tell her that she loved her. It was awkward, but she did. The girl melted. They both cried. They were friends again. It works!
"Do not be overcome by evil,
but overcome evil with good."
Romans 12:21 NASB
May they always be a source of God-honoring encouragement to one another, sensitive to one another's weaknesses or insecurities. May they hold one another accountable in their passions for You, Your Word, Your Will, Your Wisdom, Your World (reaching the lost) and holiness.
I prayed this very dangerous and effective prayer,
Anyone who is not a part of Your sovereign plan for
my children's lives,
please grant them a holy, reverent fear of You
and my daughter (or son).
Let there be no words spoken,
no actions taken,
and no soul ties established
that might someday cause pain
as the course of their lives is directed or redirected
according to Your desire and delight.
Protect them emotionally, physically, and spiritually.
May they guard and guide their hearts and thoughts and actions
according to Your Will and Your Word.
In the beautiful and powerful and wonderful Name of Jesus
may this prayer resonate before Your holy Throne of Grace
until Your Will is wholly executed.

Matthew & Kristina ~ football game
He did not tell her he loved her nor did he kiss her for almost a year -
until he was ready to take her as his wife.
Matthew lives up to his name, meaning "Gift from God."
When they married, her "something blue" was on the lining of her dress,
Psalm 37:4.
(Delight yourself in the Lord, and He will give you the desires of your heart.)
They're married and have four children.
Melissa Ann is 22 today as I post this May 24, 2016. She's saving her first kiss for her wedding day and is not currently dating anyone.
Now to Him who is able to do infinitely more
than all we ask or imagine...
Ephesians 3:20 BSB

Keep them far from any form of violent “entertainment” or “pastime” - music, video games, movies, or activities that desensitize their hearts and minds.    
Keep them far from any form of violent "entertainment" or "pastime" - music, video games, movies, or activities that desensitize their hearts and minds.    
Whenever we see a heart, may we be inspired to pray,
May they always be kind, tenderhearted,
forgiving one another just as Christ forgave us all,
faithfully following Biblical mandates for reconciliation
so that their prayers and offerings and lives
are acceptable in Your sight
(Eph. 4:32, Heb. 12:15, Matt. 5:21-24, Matt. 6:12-15).
When using a knife or scissors, may we be reminded to ask God to break any unholy alliance or to sever any friendship that will keep our children from becoming all that He desires and delights for them to be.
May our children never be unequally tied together with unbelievers, but rather live in unique distinction as children of God, leading those who are walking in darkness into Your Light and Love (2 Cor. 6:14-18). Among Christian friends, may there be no divisions, rather walking in perfect unity in mind and thought (1 Cor. 1:10), faithfully following Biblical mandates for reconciliation whenever a relationship is strained (Matt. 6:12-15).
May they and their friends be imitators of God, walking in love. May no form of sexual immorality - physical, visual, emotional - be named among them, avoiding even immoral jesting (Eph. 5:1-7)...
Blessed is the man Who walks not in the counsel of the ungodly,
Nor stands in the path of sinners,
Nor sits in the seat of the scornful;
But his delight is in the law of the Lord,
And in His law he meditates day and night.
He shall be like a tree
Planted by the rivers of water
That brings forth its fruit in its season,
Whose leaf also shall not wither;
And whatever he does shall prosper.
Psalm One NIV
 Following prayers, prayer inspirations, and prayer strategies on this website, adapt them to pray for your children's friends - asking God to work in their friends' hearts and to surround all with mentors and God-honoring individuals who will guide them and keep them on the right pathway.  
He will.